The Evolution of Microbial Life

The Evolution of Microbial Life
Chapter 15 The Evolution of Microbial Life

Biology and Society: Has Life Been Created in the Lab?
How did life first arise on Earth? To gain insight, scientists have synthesized from scratch the entire genome of a small bacterium known as Mycoplasma mycoides and transplanted the artificial genome into the cells of a closely related species called Mycoplasma capricolum. © 2013 Pearson Education, Inc. 2

Figure 15.0 Figure 15.0 These present-day rocky outcrops closely resemble fossils of prokaryotes at the dawn of life. 3

Biology and Society: Has Life Been Created in the Lab?
The newly installed genome took over the recipient cells, began cranking out M. mycoides proteins, and reproduced to make more cells containing the synthetic M. mycoides genome. © 2013 Pearson Education, Inc.

MAJOR EPISODES IN THE HISTORY OF LIFE
Earth was formed about 4.6 billion years ago. Prokaryotes evolved by about 3.5 billion years ago, began oxygen production about 2.7 billion years ago, lived alone for more than a billion years, and continue in great abundance today. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often have difficulty grasping the enormity of time. Perhaps surprisingly, many students do not understand that a billion is a thousand times greater than a million. Exercises and examples that help students comprehend such large numbers should be considered, so that students can understand these tremendous periods for evolutionary diversification. Here are just a few examples to consider: a. If an earthquake or volcano erupts just once every thousand years or so, how often will this event occur in a million years? (One thousand times.) Note that what is rare to us becomes “common” in geological terms. b. Have students calculate the age of a human when they reach their 1 billionth second of life. (Starting with birth, the answer is years.) 1,000,000,000 (seconds) = (years)  (days in a year)  24 (hours in a day)  60 (minutes)  60 (seconds). c. Then have students calculate how long it takes to live 1,000,000 seconds. (About days.) Teaching Tips 1. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall. Mark these proportional periods: The full length of time is 4.6 billion years. The percentages below were calculated using the textbook’s approximate dates for each of these events. 0.0%—The Earth forms. 13%—The Earth’s crust solidifies. 24%—The first life appears. 41%—Photosynthetic prokaryotes start producing an oxygen-rich atmosphere. 54%—The first eukaryotes appear. 74%—The first multicellular eukaryotes appear. 89%—Plants first invade land. 2. Students may need to be reminded about the reactive properties of oxygen. Note that rust is the result of oxygen interacting with iron and could be seen in the fossil record. Oxygen is highly reactive and could interfere with life-forming chemical processes today. 5

Single-celled eukaryotes first evolved about 2.1 billion years ago. Multicellular eukaryotes first evolved at least 1.2 billion years ago. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often have difficulty grasping the enormity of time. Perhaps surprisingly, many students do not understand that a billion is a thousand times greater than a million. Exercises and examples that help students comprehend such large numbers should be considered, so that students can understand these tremendous periods for evolutionary diversification. Here are just a few examples to consider: a. If an earthquake or volcano erupts just once every thousand years or so, how often will this event occur in a million years? (One thousand times.) Note that what is rare to us becomes “common” in geological terms. b. Have students calculate the age of a human when they reach their 1 billionth second of life. (Starting with birth, the answer is years.) 1,000,000,000 (seconds) = (years)  (days in a year)  24 (hours in a day)  60 (minutes)  60 (seconds). c. Then have students calculate how long it takes to live 1,000,000 seconds. (About days.) Teaching Tips 1. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall. Mark these proportional periods: The full length of time is 4.6 billion years. The percentages below were calculated using the textbook’s approximate dates for each of these events. 0.0%—The Earth forms. 13%—The Earth’s crust solidifies. 24%—The first life appears. 41%—Photosynthetic prokaryotes start producing an oxygen-rich atmosphere. 54%—The first eukaryotes appear. 74%—The first multicellular eukaryotes appear. 89%—Plants first invade land. 2. Students may need to be reminded about the reactive properties of oxygen. Note that rust is the result of oxygen interacting with iron and could be seen in the fossil record. Oxygen is highly reactive and could interfere with life-forming chemical processes today. 6

Ancestor to all present-day life
Figure 15.1a Precambrian Ancestor to all present-day life Atmospheric oxygen begins to appear Origin of Earth Earth’s crust solidifies Oldest prokaryotic fossils 4,500 4,000 3,500 3,000 2,500 Millions of years ago Figure 15.1 Some major episodes in the history of life (part 1) 7

8 Precambrian Oldest eukaryotic fossils
Figure 15.1b Precambrian Oldest eukaryotic fossils Origin of multicellular organisms Oldest animal fossils 2,000 1,500 1,000 Millions of years ago Figure 15.1 Some major episodes in the history of life (part 2) 8

9 Precambrian Paleozoic Cenozoic Bacteria Prokaryotes Archaea Protists
Figure 15.1c Precambrian Paleozoic Meso- zoic Cenozoic Bacteria Prokaryotes Archaea Protists Eukaryotes Plants Fungi Animals Cambrian explosion Extinction of dinosaurs Oldest animal fossils Plants colonize land First humans 1,000 500 Millions of years ago Figure 15.1 Some major episodes in the history of life (part 3) 9

All the major phyla of animals evolved by the end of the Cambrian explosion, which began about 540 million years ago and lasted about 10 million years. Plants and fungi first colonized land about 500 million years ago and were followed by amphibians that evolved from fish. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often have difficulty grasping the enormity of time. Perhaps surprisingly, many students do not understand that a billion is a thousand times greater than a million. Exercises and examples that help students comprehend such large numbers should be considered, so that students can understand these tremendous periods for evolutionary diversification. Here are just a few examples to consider: a. If an earthquake or volcano erupts just once every thousand years or so, how often will this event occur in a million years? (One thousand times.) Note that what is rare to us becomes “common” in geological terms. b. Have students calculate the age of a human when they reach their 1 billionth second of life. (Starting with birth, the answer is years.) 1,000,000,000 (seconds) = (years)  (days in a year)  24 (hours in a day)  60 (minutes)  60 (seconds). c. Then have students calculate how long it takes to live 1,000,000 seconds. (About days.) Teaching Tips 1. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall. Mark these proportional periods: The full length of time is 4.6 billion years. The percentages below were calculated using the textbook’s approximate dates for each of these events. 0.0%—The Earth forms. 13%—The Earth’s crust solidifies. 24%—The first life appears. 41%—Photosynthetic prokaryotes start producing an oxygen-rich atmosphere. 54%—The first eukaryotes appear. 74%—The first multicellular eukaryotes appear. 89%—Plants first invade land. 2. Students may need to be reminded about the reactive properties of oxygen. Note that rust is the result of oxygen interacting with iron and could be seen in the fossil record. Oxygen is highly reactive and could interfere with life-forming chemical processes today. 10

What if we use a clock analogy to tick down all of the major events in the history of life on Earth? © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often have difficulty grasping the enormity of time. Perhaps surprisingly, many students do not understand that a billion is a thousand times greater than a million. Exercises and examples that help students comprehend such large numbers should be considered, so that students can understand these tremendous periods for evolutionary diversification. Here are just a few examples to consider: a. If an earthquake or volcano erupts just once every thousand years or so, how often will this event occur in a million years? (One thousand times.) Note that what is rare to us becomes “common” in geological terms. b. Have students calculate the age of a human when they reach their 1 billionth second of life. (Starting with birth, the answer is years.) 1,000,000,000 (seconds) = (years)  (days in a year)  24 (hours in a day)  60 (minutes)  60 (seconds). c. Then have students calculate how long it takes to live 1,000,000 seconds. (About days.) Teaching Tips 1. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall. Mark these proportional periods: The full length of time is 4.6 billion years. The percentages below were calculated using the textbook’s approximate dates for each of these events. 0.0%—The Earth forms. 13%—The Earth’s crust solidifies. 24%—The first life appears. 41%—Photosynthetic prokaryotes start producing an oxygen-rich atmosphere. 54%—The first eukaryotes appear. 74%—The first multicellular eukaryotes appear. 89%—Plants first invade land. 2. Students may need to be reminded about the reactive properties of oxygen. Note that rust is the result of oxygen interacting with iron and could be seen in the fossil record. Oxygen is highly reactive and could interfere with life-forming chemical processes today. 11

12 Humans nd of la on ati iz on Col Animals tes yo Origin of solar
Figure 15.2 Humans nd of la on ati iz on Col Animals tes yo Origin of solar system and Earth ar euk ar ul ll P r e s e n t ce ti Mul 1 4 tes yo kar o otes B i g l l i a eu o n r s s o f y e a 2 3 kary d le Pro el -c le At ng mo Si sp he ri c ox yg en Figure 15.2 A clock analogy for the major events in the history of life on Earth 12

THE ORIGIN OF LIFE We may never know for sure how life on Earth began.
© 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 13

Resolving the Biogenesis Paradox
All life today arises by the reproduction of preexisting life, or biogenesis. If this is true, how could the first organisms arise? From the time of the ancient Greeks until well into the 1800s, it was commonly believed that life regularly arises from nonliving matter, an idea called spontaneous generation. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 14

Resolving the Biogenesis Paradox
Today, most biologists think it is possible that life on early Earth evolved from simple cells produced by chemical and physical processes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 15

Figure 15.3 Figure 15.3 An artist’s rendition of Earth about 3 billion years ago 16

A Four-Stage Hypothesis for the Origin of Life
According to one hypothesis, the first organisms were products of chemical evolution in four stages. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 17

Stage 1: Abiotic Synthesis of Organic Monomers
The first stage in the origin of life was the first to be extensively studied in the laboratory. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 18

The Process of Science: Can Biological Monomers Form Spontaneously?
Observation: Modern biological macromolecules are all composed of elements that were present in abundance on early Earth. Question: Could biological molecules arise spontaneously under conditions like those on early Earth? © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 19

Hypothesis: A closed system designed to simulate early Earth conditions could produce biologically important organic molecules from inorganic ingredients. Prediction: Organic molecules would form and accumulate. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 20

Experiment: An apparatus was built to mimic the early Earth atmosphere and included hydrogen gas (H2), methane (CH4), ammonia (NH3), and water vapor (H2O), sparks that were discharged into the chamber to mimic the prevalent lightning of early Earth, and a condenser that cooled the atmosphere, causing water and dissolved compounds to “rain” into the miniature “sea.” © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 21

22 CH4 “Atmosphere” Water vapor NH3 H2 Electrode Condenser Cold water
Figure 15.4 CH4 “Atmosphere” Water vapor NH3 H2 Electrode Condenser Cold water H2O Cooled water containing organic molecules “Sea” Sample for chemical analysis Miller and Urey’s experiment Figure 15.4 The abiotic production of organic molecules: a laboratory simulation of early-Earth chemistry 22

Results: After the apparatus had run for a week, an abundance of organic molecules essential for life had collected in the “sea,” including amino acids, the monomers of proteins. These laboratory experiments have been repeated and extended by other scientists and support the idea that organic molecules could have arisen abiotically on early Earth. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 23

Stage 2: Abiotic Synthesis of Polymers
Researchers have brought about the polymerization of monomers to form polymers, such as proteins and nucleic acids, by dripping solutions of organic monomers onto hot sand, clay, or rock. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 24

Stage 3: Formation of Pre-Cells
A key step in the origin of life was the isolation of a collection of abiotically created molecules within a membrane. Laboratory experiments demonstrate that pre-cells could have formed spontaneously from abiotically produced organic compounds. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 25

Stage 3: Formation of Pre-Cells
Such pre-cells produced in the laboratory display some lifelike properties. They have a selectively permeable surface, can grow by absorbing molecules from their surroundings, and swell or shrink when placed in solutions of different salt concentrations. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 26

Stage 4: Origin of Self-Replicating Molecules
Life is defined partly by the process of inheritance, which is based on self-replicating molecules. One hypothesis is that the first genes were short strands of RNA that replicated themselves without the assistance of proteins, perhaps using RNAs that can act as enzymes, called ribozymes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 27

28 Original “gene” RNA monomers
Figure Original “gene” RNA monomers Formation of short RNA polymers: simple “genes” Assembly of a complementary RNA chain The complementary chain serves as a template of the original “gene.” Figure 15.5 Self-replication of RNA “genes” (step 4) 28

From Chemical Evolution to Darwinian Evolution
Over millions of years natural selection favored the most efficient pre-cells and the first prokaryotic cells evolved. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology. 2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking. Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing. Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time. Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion. 2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages. 3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align. 4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life. 5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.) 29

PROKARYOTES Prokaryotes lived and evolved all alone on Earth for about 2 billion years. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 30

They’re Everywhere! Prokaryotes are found wherever there is life,
have a collective biomass that is at least ten times that of all eukaryotes, thrive in habitats too cold, too hot, too salty, too acidic, or too alkaline for any eukaryote, cause about half of all human diseases, and are more commonly benign or beneficial. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 31

Figure 15.6 Figure 15.6 A window to early life? 32

They’re Everywhere! Compared to eukaryotes, prokaryotes are
much more abundant and typically much smaller. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 33

Figure 15.7 Colorized SEM Figure 15.7 Bacteria on the point of a pin 34

They’re Everywhere! Prokaryotes living in soil and at the bottom of lakes, rivers, and oceans help to decompose dead organisms and other organic waste material, returning vital chemical elements to the environment. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 35

The Structure and Function of Prokaryotes
Prokaryotic cells lack a membrane-enclosed nucleus, lack other membrane-enclosed organelles, typically have cell walls exterior to their plasma membranes, but display an enormous range of diversity. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 36

37 Plasma membrane Cell wall Capsule Prokaryotic flagellum Ribosomes
Figure 4.4 Plasma membrane Cell wall Capsule Prokaryotic flagellum Ribosomes Nucleoid Pili Colorized TEM Figure 4.4 An idealized prokaryotic cell 37

38 Ribosomes Centriole Not in most plant cells Cytoskeleton Lysosome
Figure 4.5 Ribosomes Centriole Not in most plant cells Cytoskeleton Lysosome Plasma membrane Nucleus Mitochondrion Rough endoplasmic reticulum (ER) Smooth endoplasmic reticulum (ER) Golgi apparatus Idealized animal cell Cytoskeleton Mitochondrion Central vacuole Cell wall Not in animal cells Nucleus Chloroplast Rough endoplasmic reticulum (ER) Ribosomes Plasma membrane Smooth endoplasmic reticulum (ER) Channels between cells Idealized plant cell Golgi apparatus Figure 4.5 A view of an idealized animal cell and plant cell 38

The three most common shapes of prokaryotes are
Prokaryotic Forms The three most common shapes of prokaryotes are spherical (cocci), rod-shaped (bacilli), and spiral or curved. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 39

40 SHAPES OF PROKARYOTIC CELLS Spherical (cocci) Rod-shaped (bacilli)
Figure 15.8 SHAPES OF PROKARYOTIC CELLS Spherical (cocci) Rod-shaped (bacilli) Spiral Colorized SEM Colorized SEM Colorized TEM Figure 15.8 Three common shapes of prokaryotic cells 40

All prokaryotes are unicellular. Some species
Prokaryotic Forms All prokaryotes are unicellular. Some species exist as groups of two or more cells, exhibit a simple division of labor among specialized cell types, or are very large, dwarfing most eukaryotic cells. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 41

42 (a) Actinomycete (b) Cyanobacteria (c) Giant bacterium
Figure 15.9 Colorized SEM (a) Actinomycete LM LM (b) Cyanobacteria (c) Giant bacterium Figure 15.9 A diversity of prokaryotic shapes and sizes 42

43 (c) Giant bacterium LM Figure 15.9c
Figure 15.9 A diversity of prokaryotic shapes and sizes (part 3) 43

Prokaryotic Forms About half of all prokaryotes are mobile, and many of these travel using one or more flagella. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 44

Prokaryotic Forms In many natural environments, prokaryotes attach to surfaces in a highly organized colony called a biofilm, which may consist of one or several species of prokaryotes, may include protists and fungi, can show a division of labor and defense against invaders, and © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 45

Prokaryotic Forms can form on almost any type of surface, including
rocks, metal, plastic, and organic material including teeth. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 46

Figure 15.10 Colorized SEM Figure Dental plaque, a biofilm that forms on teeth 47

Prokaryotic Reproduction
Most prokaryotes can reproduce by dividing in half by binary fission and at very high rates if conditions are favorable. Some prokaryotes form endospores, which are thick-coated, protective cells produced when the prokaryote is exposed to unfavorable conditions. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 48

49 Endospore Colorized TEM Figure 15.11
Figure An endospore in an anthrax bacterium 49

Prokaryotic Nutrition
Biologists use the phrase “mode of nutrition” to describe how organisms obtain energy and carbon. Energy Phototrophs obtain energy from light. Chemotrophs obtain energy from environmental chemicals. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 50

Carbon Autotrophs obtain carbon from carbon dioxide (CO2). Heterotrophs obtain carbon from at least one organic nutrient—the sugar glucose, for instance. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 51

We can group all organisms according to the four major modes of nutrition if we combine the energy source (phototroph versus chemotroph) and carbon source (autotroph versus heterotroph). © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 52

Dominant among multicellular organisms are photoautotrophs and chemoheterotrophs. The other two modes are used only by certain prokaryotes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 53

54 MODES OF NUTRITION Energy source Light Chemical CO2 Carbon source
Figure 15.12 MODES OF NUTRITION Energy source Light Chemical Photoautotrophs Chemoautotrophs Colorized TEM CO2 Elodea, an aquatic plant Bacteria from a hot spring Carbon source Photoheterotrophs Chemoheterotrophs Colorized TEM Organic compounds Rhodopseudomonas Kingfisher with prey Figure Modes of nutrition 54

The Two Main Branches of Prokaryotic Evolution: Bacteria and Archaea
By comparing diverse prokaryotes at the molecular level, biologists have identified two major branches of prokaryotic evolution: bacteria and archaea (more closely related to eukaryotes). © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 55

Thus, life is organized into three domains: Bacteria, Archaea, and Eukarya. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 56

Some archaea are “extremophiles.” Halophiles thrive in salty environments. Thermophiles inhabit very hot water. Methanogens inhabit the bottoms of lakes and swamps and aid digestion in cattle and deer. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 57

58 (a) Salt-loving archaea (b) Heat-loving archaea Figure 15.13
Figure Archaeal “extremophiles” 58

Bacteria and Disease Bacteria That Cause Disease
Bacteria and other organisms that cause disease are called pathogens. Most pathogenic bacteria produce poisons. Exotoxins are proteins bacterial cells secrete into their environment. Endotoxins are not cell secretions but instead chemical components of the outer membrane of certain bacteria. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 59

60 Haemophilus influenzae Cells of nasal lining Colorized SEM
Figure 15.14 Colorized SEM Haemophilus influenzae Cells of nasal lining Figure Bacteria that cause pneumonia 60

Bacteria That Cause Disease
The best defenses against bacterial disease are sanitation, antibiotics, and education. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 61

Bacteria That Cause Disease
Lyme disease is caused by bacteria carried by ticks and treated with antibiotics, if detected early. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 62

63 Tick that carries the Lyme disease bacterium Spirochete that causes
Figure 15.15 SEM Tick that carries the Lyme disease bacterium Spirochete that causes Lyme disease “Bull’s-eye” rash Figure Lyme disease, a bacterial disease transmitted by ticks 63

64 “Bull’s-eye” rash Figure 15.15a
Figure Lyme disease, a bacterial disease transmitted by ticks (part 1) 64

65 Tick that carries the Lyme disease bacterium Figure 15.15b

66 Tick that carries the Lyme disease bacterium Figure 15.15c

67 Spirochete that causes Lyme disease SEM Figure 15.15d

Five people died from this attack.
Biological Weapons In October 2001, endospores of the bacterium that causes anthrax were mailed to members of the news media and the U.S. Senate. Five people died from this attack. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 68

Biological Weapons Another bacterium considered to have dangerous potential as a weapon is Clostridium botulinum, producer of the exotoxin botulinum, which blocks transmission of nerve signals that cause muscle contraction and is the deadliest poison on Earth. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 69

The bacterium that causes plague
Biological Weapons The bacterium that causes plague is also a potential biological weapon, is carried by rodents, and transmitted by fleas, produces egg-size swellings called buboes under the skin, and can be treated with antibiotics if diagnosed early. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 70

Figure 15.16 Figure Swellings characteristic of bubonic plague 71

The Ecological Impact of Prokaryotes
Pathogenic bacteria are in the minority among prokaryotes. Far more common are species that are essential to our well-being, either directly or indirectly. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 72

Prokaryotes and Chemical Recycling
Prokaryotes play essential roles in chemical cycles in the environment and the breakdown of organic wastes and dead organisms. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 73

Prokaryotes and Bioremediation
Bioremediation is the use of organisms to remove pollutants from water, air, and soil. A familiar example is the use of prokaryotic decomposers in sewage treatment. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 74

75 Rotating arm spraying liquid wastes Rock bed coated with aerobic
Figure 15.17 Rotating arm spraying liquid wastes Rock bed coated with aerobic prokaryotes and fungi Outflow Liquid wastes Figure Putting microbes to work in sewage treatment facilities 75

Prokaryotes and Bioremediation
Certain bacteria can decompose petroleum and are useful in cleaning up oil spills. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.” After all, what eukaryotes can survive in the habitats of extremophiles? 2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. 3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells. 4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated. 5. Students may believe that we have already documented the diversity of life on Earth. However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. 2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture. The construction of these diverse shapes might also make for a quick lab activity. 3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have you pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month! 4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, etc.) They can then write a short summary or the website address to you for your inspection. 5. Chemoautotrophs permit ecosystems which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception. 6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico. 7. The website is a good source for information on bioremediation. 8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. 9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions. 76

Figure 15.18 Figure Treatment of an oil spill in Alaska 77

PROTISTS Protists are eukaryotes that are not fungi, animals, or plants, mostly unicellular, and ancestral to all other eukaryotes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 78

The Origin of Eukaryotic Cells
Eukaryotic cells evolved by the infolding of the plasma membrane of a prokaryotic cell to form the endomembrane system and a process known as endosymbiosis. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 79

The Origin of Eukaryotic Cells
Symbiosis is a more general association between organisms of two or more species. Endosymbiosis refers to one species living inside another host species and is the process by which eukaryotes gained mitochondria and chloroplasts. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 80

81 (a) Origin of the endomembrane system
Figure 15.19 Plasma membrane Photosynthetic prokaryote DNA Membrane infolding Cytoplasm Endosymbiosis Aerobic heterotrophic prokaryote Endoplasmic reticulum Ancestral prokaryote Chloroplast Nucleus Nuclear envelope Mitochondrion Cell with nucleus and endomembrane system Photosynthetic eukaryotic cell (a) Origin of the endomembrane system (b) Origin of mitochondria and chloroplasts Figure A two-stage hypothesis for the evolution of eukaryotes through endosymbiosis 81

The Diversity of Protists
The group called protists consists of multiple clades but remains a convenient term to refer to eukaryotes that are not plants, animals, or fungi. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 82

Protists obtain their nutrition in a variety of ways. Algae are autotrophs, producing their food by photosynthesis. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 83

Other protists are heterotrophs. Some protists eat bacteria or other protists. Other protists are fungus-like and obtain organic molecules by absorption. Parasites derive their nutrition from a living host, which is harmed by the interaction. Parasitic trypanosomes infect blood and cause sleeping sickness. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 84

85 (a) An autotroph: Caulerpa, a multicellular alga
Figure 15.20 Colorized SEM LM (a) An autotroph: Caulerpa, a multicellular alga (b) A heterotroph: parasitic trypanosome (c) A mixotroph: Euglena Figure Protist modes of nutrition 85

Protist habitats are diverse and include oceans, lakes, and ponds, damp soil and leaf litter, and the bodies of host organisms with which they share mutually beneficial relationships, such as unicellular algae and reef-building coral animals, and cellulose-digesting protists and termites. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 86

Figure 15.21 LM Figure A diversity of protists in a drop of pond water 87

Protists that live primarily by ingesting food are called protozoans.
© 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 88

89 A flagellate: Giardia Another flagellate: Trichomonas An amoeba
Figure 15.22 Colorized SEM Colorized SEM Colorized TEM A flagellate: Giardia Another flagellate: Trichomonas An amoeba Apical complex Cilia Red blood cell Cell “mouth” LM TEM LM A foram An apicomplexan A ciliate Figure A diversity of protozoans 89

Protozoans with flagella are called flagellates and
are typically free-living, but some are nasty parasites. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 90

A flagellate: Giardia 91 Colorized SEM Figure 15.22a
Figure A diversity of protozoans (part 1) 91

A flagellate: Trichomonas
Figure 15.22b Colorized SEM A flagellate: Trichomonas Figure A diversity of protozoans (part 2) 92

Amoebas are characterized by
Protozoans Amoebas are characterized by great flexibility in their body shape and the absence of permanent organelles for locomotion. Most species move and feed by means of pseudopodia (singular, pseudopodium), temporary extensions of the cell. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 93

An amoeba 94 Colorized TEM Figure 15.22c

Protozoans Other protozoans with pseudopodia include the forams, which have shells. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 95

Figure 15.22d LM A foram Figure A diversity of protozoans (part 4) 96

Protozoans Apicomplexans are
named for a structure at their apex (tip) that is specialized for penetrating host cells and tissues, all parasitic, and able to cause serious human diseases, such as malaria caused by Plasmodium. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 97

Apical complex Red blood cell An apicomplexan 98 TEM Figure 15.22e

Another apicomplexan is Toxoplasma,
Protozoans Another apicomplexan is Toxoplasma, occurring in the digestive tracts of millions of people in the United States but held in check by the immune system. A woman newly infected with Toxoplasma during pregnancy can pass the parasite to her unborn child, who may suffer nervous system damage. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 99

Ciliates are protozoans that
are named for their use of hair-like structures called cilia to move and sweep food into their mouths, are mostly free-living (nonparasitic), such as the freshwater ciliate Paramecium, and include heterotrophs and mixotrophs. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 100

Cilia Cell “mouth” A ciliate 101 LM Figure 15.22f

The two main groups of these protists are
Slime Molds Slime molds resemble fungi in appearance and lifestyle due to convergence, but are more closely related to amoebas. The two main groups of these protists are plasmodial slime molds and cellular slime molds. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 102

Plasmodial slime molds
are named for the feeding stage in their life cycle, an amoeboid mass called a plasmodium, are decomposers on forest floors, and can be large. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 103

A plasmodial slime mold
Figure 15.23 A plasmodial slime mold Figure A plasmodial slime mold 104

Slime Molds Cellular slime molds have an interesting and complex life cycle of successive stages: a feeding stage of solitary amoeboid cells, a swarming stage as a slug-like colony that can move and function as a single unit, and a stage during which they generate a stalk-like multicellular reproductive structure. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 105

106 Life stages of a cellular slime mold 2 Slug-like colony 1
Figure 15.24 Life stages of a cellular slime mold 2 Slug-like colony LM 1 Amoeboid cells 3 Reproductive structure Figure Life stages of a cellular slime mold 106

Unicellular and Colonial Algae
Algae are photosynthetic protists whose chloroplasts support food chains in freshwater and marine ecosystems. Many unicellular algae are components of plankton, the communities of mostly microscopic organisms that drift or swim weakly in aquatic environments. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 107

Unicellular algae include dinoflagellates, with two beating flagella and external plates made of cellulose, diatoms, with glassy cell walls containing silica, and green algae. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society.

Green algae are unicellular in most freshwater lakes and ponds, sometimes flagellated, such as Chlamydomonas, and sometimes colonial, forming a hollow ball of flagellated cells as seen in Volvox. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society.

110 (a) A dinoflagellate, with its wall of protective plates
Figure 15.25 SEM LM (a) A dinoflagellate, with its wall of protective plates (b) A sample of diverse diatoms, which have glassy walls Colorized SEM LM (c) Chlamydomonas, a unicellular green alga with a pair of flagella (d) Volvox, a colonial green alga Figure Unicellular and colonial algae 110

Seaweeds Seaweeds are large, multicellular marine algae,
grow on or near rocky shores, are only similar to plants because of convergent evolution, are most closely related to unicellular algae, and are often edible. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 111

Seaweeds Seaweeds are classified into three different groups, based partly on the types of pigments present in their chloroplasts: green algae, red algae, and brown algae (including kelp). © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 112

113 Green algae Red algae Brown algae Figure 15.26
Figure The three major groups of seaweeds 113

Evolution Connection: The Origin of Multicellular Life
Multicellular organisms have specialized cells that are dependent on each other and perform different functions, such as feeding, waste disposal, gas exchange, and protection. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 114

Evolution Connection: The Origin of Multicellular Life
Colonial protists likely formed the evolutionary links between unicellular and multicellular organisms. The colonial green alga Volvox demonstrates one level of specialization and cooperation. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells. 2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals. 3. Students might immediately expect that all symbiotic relationships benefit both members. Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed. 4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night. Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes. 2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons. 3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject. 4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.) 5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science. 6. The evolution of multicellularity requires the subdivision of labor in ways ｭsimilar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society. 115

Figure An ancestral colony may have formed when a cell divided and remained attached to its offspring. Additional specialization may have led to sex cells (gametes) and nonreproductive cells (somatic cells). Cells in the colony may have become specialized and interdependent. Unicellular protist Gamete Food- synthesizing cells Somatic cells Locomotor cells Figure A model for the evolution of multicellular organisms from unicellular protists (step 3) 116

Bacteria Prokaryotes Archaea Protists Eukarya Plants Fungi Animals 117
Figure 15.UN01 Bacteria Prokaryotes Archaea Protists Eukarya Plants Fungi Animals Figure 15.UN01 In-text figure, prokaryote mini-tree, p. 300 117

118 Major episode Millions of years ago Plants and fungi colonize land
Figure 15.UN03 Major episode Millions of years ago Plants and fungi colonize land 500 All major animal phyla established 530 First multicellular organisms 1,200 Oldest eukaryotic fossils 1,800 Accumulation of O2 in atmosphere 2,400 Oldest prokaryotic fossils 3,500 Origin of Earth 4,600 Figure 15.UN03 Summary of Key Concepts: Major Episodes in the History of Life 118

119 Inorganic compounds Abiotic synthesis of organic monomers
Figure 15.UN04 Inorganic compounds 1 Abiotic synthesis of organic monomers Organic monomers 2 Abiotic synthesis of polymers Polymer 3 Formation of pre-cells Membrane-enclosed compartment 4 Self-replicating molecules Complementary chain Figure 15.UN04 Summary of Key Concepts: A Four-Stage Hypothesis for the Origin of Life 119

Spherical Rod-shaped Spiral 120 Figure 15.UN05
Figure 15.UN05 Summary of Key Concepts: The Structure and Function of Prokaryotes 120

121 Nutritional Mode Energy Source Carbon Source Photoautotroph
Figure 15.UN06 Nutritional Mode Energy Source Carbon Source Photoautotroph Sunlight CO2 Chemoautotroph Inorganic chemicals Photoheterotroph Sunlight Organic compounds Chemoheterotroph Organic compounds Figure 15.UN06 Summary of Key Concepts: Modes of Nutrition 121

The Evolution of Microbial Life

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