Microbial Life: Prokaryotes and Protists

Microbial Life: Prokaryotes and Protists
Chapter 16 Microbial Life: Prokaryotes and Protists

Figure 16.0_1 Figure 16.0_1 Unit Four: The Evolution of Biological Diversity (Nudibranch) 2

Chapter 16: Big Ideas Prokaryotes Protists Figure 16.0_2
Figure 16.0_2 Chapter 16: Big Ideas Prokaryotes Protists 3

Figure 16.0_3 Figure 16.0_3 The biodiversity of a coral reef 4

16.1 Prokaryotes are diverse and widespread
Prokaryotic cells are smaller than eukaryotic cells. Prokaryotes range from 1–5 µm in diameter. Eukaryotes range from 10–100 µm in diameter. The collective biomass of prokaryotes is at least 10 times that of all eukaryotes. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one- billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips 1. Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. 2. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 3. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall, marking it proportionally as follows: 0.0%: Earth forms. (4.6 billion years ago) 13%: Earth’s crust solidifies. (4 billion years ago) 15–25%: The first life appears. (3.5–3.9 billion years ago) 41%: Photosynthetic prokaryotes start producing an oxygen-rich atmosphere. (2.7 billion years ago) 54%: The first eukaryotes appear. (2.1 billion years ago) 67%: The first multicellular eukaryotes appear. (1.5 billion years ago) 89%: Plants first invade land. (500 million years ago) 99.9%: Human and ape ancestries diverge! (6–7 million years ago) 4. Remind students that the term bacteria is not equivalent to the term prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. © 2012 Pearson Education, Inc. 6

Figure 16.1 Figure 16.1 Bacteria on the point of a pin 7

Prokaryotes live in habitats too cold, too hot, too salty, too acidic, and too alkaline for eukaryotes to survive. Some bacteria are pathogens, causing disease. But most bacteria on our bodies are benign or beneficial. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips 1. Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. 2. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 3. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall, marking it proportionally as follows: 0.0%: Earth forms. (4.6 billion years ago) 13%: Earth’s crust solidifies. (4 billion years ago) 15–25%: The first life appears. (3.5–3.9 billion years ago) 41%: Photosynthetic prokaryotes start producing an oxygen-rich atmosphere. (2.7 billion years ago) 54%: The first eukaryotes appear. (2.1 billion years ago) 67%: The first multicellular eukaryotes appear. (1.5 billion years ago) 89%: Plants first invade land. (500 million years ago) 99.9%: Human and ape ancestries diverge! (6–7 million years ago) 4. Remind students that the term bacteria is not equivalent to the term prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. © 2012 Pearson Education, Inc. 8

Several hundred species of bacteria live in and on our bodies, decomposing dead skin cells, supplying essential vitamins, and guarding against pathogenic organisms. Prokaryotes in soil decompose dead organisms, sustaining chemical cycles. Student Misconceptions and Concerns 1 Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips 1. Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. 2. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 3. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall, marking it proportionally as follows: 0.0%: Earth forms. (4.6 billion years ago) 13%: Earth’s crust solidifies. (4 billion years ago) 15–25%: The first life appears. (3.5–3.9 billion years ago) 41%: Photosynthetic prokaryotes start producing an oxygen-rich atmosphere. (2.7 billion years ago) 54%: The first eukaryotes appear. (2.1 billion years ago) 67%: The first multicellular eukaryotes appear. (1.5 billion years ago) 89%: Plants first invade land. (500 million years ago) 99.9%: Human and ape ancestries diverge! (6–7 million years ago) 4. Remind students that the term bacteria is not equivalent to the term prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction. © 2012 Pearson Education, Inc. 9

16.2 External features contribute to the success of prokaryotes
Prokaryotic cells have three common cell shapes. Cocci are spherical prokaryotic cells. They sometimes occur in chains that are called streptococci. Bacilli are rod-shaped prokaryotes. Bacilli may also be threadlike, or filamentous. Spiral prokaryotes are like a corkscrew. Short and rigid prokaryotes are called spirilla. Longer, more flexible cells are called spirochetes. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Some modeling clay (oil-based clay 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 can also make for a quick lab activity. Module 16.2 provides a broad spectrum of bacterial form and function. If you are selectively assigning chapters, consider this module of high importance. © 2012 Pearson Education, Inc. 10

Cocci Bacilli Spirochete Figure 16.2A Figure 16.2A Prokaryote shapes
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Cocci Figure 16.2A_1 Figure 16.2A_1 Prokaryote shapes: cocci (part 1)
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Figure 16.2A_2 Figure 16.2A_2 Prokaryote shapes: bacilli (part 2) Bacilli 13

Figure 16.2A_3 Figure 16.2A_3 Prokaryote shapes: spirochete (part 3) Spirochete 14

Nearly all prokaryotes have a cell wall. Cell walls provide physical protection and prevent the cell from bursting in a hypotonic environment. When stained with Gram stain, cell walls of bacteria are either Gram-positive, with simpler cell walls containing peptidoglycan, or Gram-negative, with less peptidoglycan, and more complex and more likely to cause disease. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Some modeling clay (oil-based clay 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 can also make for a quick lab activity. Module 16.2 provides a broad spectrum of bacterial form and function. If you are selectively assigning chapters, consider this module of high importance. © 2012 Pearson Education, Inc. 15

Figure 16.2B Figure 16.2B Gram-positive (purple) and gram-negative (pink) bacteria 16

The cell wall of many prokaryotes is covered by a capsule, a sticky layer of polysaccharides or protein. The capsule enables prokaryotes to adhere to their substrate or to other individuals in a colony and shields pathogenic prokaryotes from attacks by a host’s immune system. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Some modeling clay (oil-based clay 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 can also make for a quick lab activity. Module 16.2 provides a broad spectrum of bacterial form and function. If you are selectively assigning chapters, consider this module of high importance. © 2012 Pearson Education, Inc. 17

Figure 16.2C Tonsil cell Capsule Figure 16.2C Capsule Bacterium 18

Some prokaryotes have external structures that extend beyond the cell wall. Flagella help prokaryotes move in their environment. Hairlike projections called fimbriae enable prokaryotes to stick to their substrate or each other. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Some modeling clay (oil-based clay 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 can also make for a quick lab activity. Module 16.2 provides a broad spectrum of bacterial form and function. If you are selectively assigning chapters, consider this module of high importance. © 2012 Pearson Education, Inc. 19

Figure 16.2D Flagella Figure 16.2D Flagella and fimbriae Fimbriae 20

16.3 Populations of prokaryotes can adapt rapidly to changes in the environment
Prokaryote population growth occurs by binary fission, can rapidly produce a new generation within hours, and can generate a great deal of genetic variation by spontaneous mutations, increasing the likelihood that some members of the population will survive changes in the environment. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather have a million dollars or start out with just a penny and have it doubled every day for a month?” Choosing the doubling amount pays off at about $10 million. Students may need help thinking through why short generation times and large numbers of offspring permit rapid evolution. The authors address this important aspect of evolution in Module However, students may need additional clarity and examples to better understand the speed of evolutionary change permitted in bacteria as compared to long-lived organisms such as whales, elephants, and humans. © 2012 Pearson Education, Inc. 21

The genome of a prokaryote typically has about one-thousandth as much DNA as a eukaryotic genome and is one long, circular chromosome packed into a distinct region of the cell. Many prokaryotes also have additional small, circular DNA molecules called plasmids, which replicate independently of the chromosome. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather have a million dollars or start out with just a penny and have it doubled every day for a month?” Choosing the doubling amount pays off at about $10 million. Students may need help thinking through why short generation times and large numbers of offspring permit rapid evolution. The authors address this important aspect of evolution in Module However, students may need additional clarity and examples to better understand the speed of evolutionary change permitted in bacteria as compared to long-lived organisms such as whales, elephants, and humans. © 2012 Pearson Education, Inc. 22

Chromosome Plasmids Figure 16.3A
Figure 16.3A DNA released from a ruptured bacterial cell 23

Some prokaryotes form specialized cells called endospores that remain dormant through harsh conditions. Endospores can survive extreme heat or cold. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather have a million dollars or start out with just a penny and have it doubled every day for a month?” Choosing the doubling amount pays off at about $10 million. Students may need help thinking through why short generation times and large numbers of offspring permit rapid evolution. The authors address this important aspect of evolution in Module However, students may need additional clarity and examples to better understand the speed of evolutionary change permitted in bacteria as compared to long-lived organisms such as whales, elephants, and humans. © 2012 Pearson Education, Inc. 24

Figure 16.3B Endospore Figure 16.3B An endospore within an anthrax bacterium cell 25

16.4 Prokaryotes have unparalleled nutritional diversity
Prokaryotes exhibit much more nutritional diversity than eukaryotes. Two sources of energy are used. Phototrophs capture energy from sunlight. Chemotrophs harness the energy stored in chemicals. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Consider asking students to examine the four modes of nutrition presented in Figure Then, predict which of the four modes of nutrition are typically used by (a) plants, (b) animals, and (c) fungi. Unusual exceptions to these patterns are also an opportunity for some critical thinking. Chemoautotrophs permit ecosystems that do not rely upon 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 upon photosynthesis. Chemoautotrophs are an exception. © 2012 Pearson Education, Inc. 26

Two sources of carbon are used by prokaryotes. Autotrophs obtain carbon atoms from carbon dioxide. Heterotrophs obtain their carbon atoms from the organic compounds present in other organisms. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Consider asking students to examine the four modes of nutrition presented in Figure Then, predict which of the four modes of nutrition are typically used by (a) plants, (b) animals, and (c) fungi. Unusual exceptions to these patterns are also an opportunity for some critical thinking. Chemoautotrophs permit ecosystems that do not rely upon 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 upon photosynthesis. Chemoautotrophs are an exception. © 2012 Pearson Education, Inc. 27

The terms that describe how prokaryotes obtain energy and carbon are combined to describe their modes of nutrition. Photoautotrophs obtain energy from sunlight and use carbon dioxide for carbon. Photoheterotrophs obtain energy from sunlight but get their carbon atoms from organic molecules. Chemoautotrophs harvest energy from inorganic chemicals and use carbon dioxide for carbon. Chemoheterotrophs acquire energy and carbon from organic molecules. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Consider asking students to examine the four modes of nutrition presented in Figure Then, predict which of the four modes of nutrition are typically used by (a) plants, (b) animals, and (c) fungi. Unusual exceptions to these patterns are also an opportunity for some critical thinking. Chemoautotrophs permit ecosystems that do not rely upon 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 upon photosynthesis. Chemoautotrophs are an exception. © 2012 Pearson Education, Inc. 28

ENERGY SOURCE CARBON SOURCE Sunlight Chemicals Photoautotrophs
Figure 16.4 ENERGY SOURCE Sunlight Chemicals Photoautotrophs Chemoautotrophs CO2 Oscilliatoria Unidentified “rock-eating” bacteria CARBON SOURCE Photoheterotrophs Chemoheterotrophs Organic compounds Figure 16.4 Sources of energy and carbon in prokaryotic modes of nutrition Rhodopseudomonas A Bdellovibrio attacking a larger cell 29

Photoautotrophs Oscilliatoria Figure 16.4_1
Figure 16.4_1 Sources of energy and carbon in prokaryotes: Oscilliatoria (part 1) Oscilliatoria 30

Photoheterotrophs Rhodopseudomonas Figure 16.4_2
Figure 16.4_2 Sources of energy and carbon in prokaryotes: Rhodopseudomonas (part 2) Rhodopseudomonas 31

Unidentified “rock-eating” bacteria
Figure 16.4_3 Chemoautotrophs Figure 16.4_3 Sources of energy and carbon in prokaryotes: “Rock-eating” bacteria (part 3) Unidentified “rock-eating” bacteria 32

A Bdellovibrio attacking a larger cell
Figure 16.4_4 Chemoheterotrophs Figure 16.4_4 Sources of energy and carbon in prokaryotes: A Bdellovibrio attacking a larger cell (part 4) A Bdellovibrio attacking a larger cell 33

16.5 CONNECTION: Biofilms are complex associations of microbes
Biofilms are complex associations of one or several species of prokaryotes and may also include protists and fungi. Prokaryotes attach to surfaces and form biofilm communities that are difficult to eradicate and may cause medical and environmental problems. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Some aspects of the complex structure and organization of biofilms are similar to eukaryotic tissues and organs. Challenge students to identify analogous components of biofilms and eukaryotic tissues and organs. © 2012 Pearson Education, Inc. 34

Biofilms are large and complex “cities” of microbes that communicate by chemical signals, coordinate a division of labor and defense against invaders, and use channels to distribute nutrients and collect wastes. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Some aspects of the complex structure and organization of biofilms are similar to eukaryotic tissues and organs. Challenge students to identify analogous components of biofilms and eukaryotic tissues and organs. © 2012 Pearson Education, Inc. 35

Biofilms that form in the environment can be difficult to eradicate. Biofilms clog and corrode pipes, gum up filters and drains, and Coat the hulls of ships. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Some aspects of the complex structure and organization of biofilms are similar to eukaryotic tissues and organs. Challenge students to identify analogous components of biofilms and eukaryotic tissues and organs. © 2012 Pearson Education, Inc. 36

Figure 16.5 Figure 16.5 A biofilm fouling the insides of a pipe 37

16.6 CONNECTION: Prokaryotes help clean up the environment
Prokaryotes are useful for cleaning up contaminants in the environment because prokaryotes have great nutritional diversity, are quickly adaptable, and can form biofilms. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. 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. is a useful website that addresses bioremediation. © 2012 Pearson Education, Inc. 38

Bioremediation is the use of organisms to remove pollutants from soil, air, or water. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. 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. is a useful website that addresses bioremediation. © 2012 Pearson Education, Inc. 39

Prokaryotic decomposers are the mainstays of sewage treatment facilities. Raw sewage is first passed through a series of screens and shredders. Solid matter then settles out from the liquid waste, forming sludge. Sludge is gradually added to a culture of anaerobic prokaryotes, including bacteria and archaea. The microbes decompose the organic matter into material that can be placed in a landfill or used as fertilizer. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. 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. is a useful website that addresses bioremediation. © 2012 Pearson Education, Inc. 40

Liquid wastes are treated separately from the sludge. Liquid wastes are sprayed onto a thick bed of rocks. Biofilms of aerobic bacteria and fungi growing on the rocks remove much of the dissolved organic material. Fluid draining from the rocks is sterilized and then released, usually into a river or ocean. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. 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. is a useful website that addresses bioremediation. © 2012 Pearson Education, Inc. 41

Rotating spray arm Rock bed coated with aerobic prokaryotes and fungi
Figure 16.6A Rotating spray arm Figure 16.6A The trickling filter system at a sewage treatment plant Rock bed coated with aerobic prokaryotes and fungi Liquid wastes Outflow 42

Figure 16.6A_1 Rotating spray arm Rock bed coated with aerobic prokaryotes and fungi Figure 16.6A_1 The trickling filter system at a sewage treatment plant (part 1) Liquid wastes Outflow 43

Figure 16.6A_2 Figure 16.6A_2 The trickling filter system at a sewage treatment plant (part 2) Rotating spray arm Rock bed coated with aerobic prokaryotes and fungi 44

Bioremediation is becoming an important tool for cleaning up toxic chemicals released into the soil and water by industrial processes. Environmental engineers change the natural environment to accelerate the activity of naturally occurring prokaryotes capable of metabolizing pollutants. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. 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. is a useful website that addresses bioremediation. © 2012 Pearson Education, Inc. 45

Figure 16.6B Figure 16.6B Treatment of an oil spill in Alaska 46

16.7 Bacteria and archaea are the two main branches of prokaryotic evolution
New studies of representative genomes of prokaryotes and eukaryotes strongly support the three-domain view of life. Prokaryotes are now classified into two domains: Bacteria and Archaea. Archaea have at least as much in common with eukaryotes as they do with bacteria. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. Students may enter your class equating the terms bacteria and prokaryotes. Module 16.7 provides a good distinction between the Bacteria and the Archaea. The relatively new distinction between the prokaryote groups Bacteria and Archaea helps to illustrate the tentative nature of science. You might wish to point out to your students that science textbooks are our understanding of biological diversity are subject to change. © 2012 Pearson Education, Inc. 47

Table 16.7 Table 16.7 Differences between the domains Bacteria, Archaea, and Eukarya 48

16.8 Archaea thrive in extreme environments—and in other habitats
Archaeal inhabitants of extreme environments have unusual proteins and other molecular adaptations that enable them to metabolize and reproduce effectively. Extreme halophiles thrive in very salty places. Extreme thermophiles thrive in very hot water, such as geysers, and acid pools. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. A Google Image search using the key words “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. © 2012 Pearson Education, Inc. 49

Figure 16.8A Figure 16.8A Orange and yellow colonies of heat-loving archaea growing in a Nevada geyser 50

16.8 Archaea thrive in extreme environments—and in other habitats
Methanogens live in anaerobic environments, give off methane as a waste product from the digestive tracts of cattle and deer and decomposing materials in landfills. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. A Google Image search using the key words “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans. © 2012 Pearson Education, Inc. 51

Figure 16.8B Figure 16.8B Pipes for collecting gas from a landfill 52

16.9 Bacteria include a diverse assemblage of prokaryotes
The domain Bacteria is currently divided into five groups, based on comparisons of genetic sequences. 1. Proteobacteria are all gram negative, share a particular rRNA sequence, and represent all four modes of nutrition. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) 5. 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. (16.9) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Chlamydia is the most common sexually transmitted disease in the United States. A rich and reliable source of information on chlamydia can be found at 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. © 2012 Pearson Education, Inc. 53

Thiomargarita namibiensis is a type of proteobacteria that is a giant among prokaryotes, typically ranging up to 100–300 microns in diameter, uses H2S to generate organic molecules from CO2, and produces sulfur wastes, seen as small greenish globules in the following figure. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) 5. 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. (16.9) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Chlamydia is the most common sexually transmitted disease in the United States. A rich and reliable source of information on chlamydia can be found at 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. © 2012 Pearson Education, Inc. 54

Figure 16.9A Figure 16.9A Thiomargarita namibiensis 55

Proteobacteria also include Rhizobium species that live symbiotically in root nodules of legumes and convert atmospheric nitrogen gas into a form usable by their legume host. Symbiosis is a close association between organisms of two or more species. Rhizobium is an endosymbiont, living within another species. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) 5. 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. (16.9) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Chlamydia is the most common sexually transmitted disease in the United States. A rich and reliable source of information on chlamydia can be found at 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. © 2012 Pearson Education, Inc. 56

Figure 32.13B Root nodules on a soybean plant
Shoot Bacteria within vesicle in an infected cell Nodules Roots Figure 32.13B Root nodules on a soybean plant 57

2. Gram-positive bacteria rival proteobacteria in diversity and include the actinomycetes common in soil. Streptomyces is often cultured by pharmaceutical companies as a source of many antibiotics. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) 5. 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. (16.9) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Chlamydia is the most common sexually transmitted disease in the United States. A rich and reliable source of information on chlamydia can be found at 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. © 2012 Pearson Education, Inc. 58

Figure 16.9B Figure 16.9B Streptomyces, the source of many antibiotics 59

3. Cyanobacteria Cyanobacteria are the only group of prokaryotes with plantlike, oxygen-generating photosynthesis. Some species, such as Anabaena, have specialized cells that fix nitrogen. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) 5. 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. (16.9) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Chlamydia is the most common sexually transmitted disease in the United States. A rich and reliable source of information on chlamydia can be found at 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. © 2012 Pearson Education, Inc. 60

Photosynthetic cells Nitrogen-fixing cells Figure 16.9C
Figure 16.9C Anabaena, a filamentous cyanobacterium 61

4. Chlamydias Chlamydias live inside eukaryotic host cells. Chlamydia trachomatis is a common cause of blindness in developing countries and is the most common sexually transmitted disease in the United States. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) 5. 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. (16.9) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Chlamydia is the most common sexually transmitted disease in the United States. A rich and reliable source of information on chlamydia can be found at 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. © 2012 Pearson Education, Inc. 62

Figure 16.9D Figure 16.9D Chlamydia cells (arrows) inside an animal cell 63

5. Spirochetes are helical bacteria and notorious pathogens, causing syphilis and Lyme disease. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) 5. 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. (16.9) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. Chlamydia is the most common sexually transmitted disease in the United States. A rich and reliable source of information on chlamydia can be found at 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. © 2012 Pearson Education, Inc. 64

Figure 16.9E Figure 16.9E Treponema pallidum, the spirochete that causes syphilis 65

16.10 CONNECTION: Some bacteria cause disease
All organisms are almost constantly exposed to pathogenic bacteria. Most bacteria that cause illness do so by producing a poison. Exotoxins are proteins that bacterial cells secrete into their environment. Endotoxins are components of the outer membrane of gram-negative bacteria. Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 2. 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 text notes that 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. 3. 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. 4. Students often have difficulty grasping geological timescales. Many students do not intuitively understand that a billion is a thousand times greater than a million. Exercises and examples such as the following may help students comprehend such large numbers. a. If an earthquake occurs or a volcano erupts once every 1,000 years, how often will one or the other take place over a million years? (Answer: 1,000 times.) Note that what is rare to us becomes common in geological terms. b. Have students calculate the age of a human when he or she reaches the one-billionth second of life (if we begin counting at birth, the answer is years). Then have them calculate how long it takes to live 1,000,000 seconds. (Answer: about 11.6 days.) Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. The many aspects of bacterial toxins often provoke student interest and can provide a rich opportunity for further student investigation. Consider having students prepare short reports on a toxin of their choice as a required or extra credit assignment. © 2012 Pearson Education, Inc. 66

Figure 16.10 Figure Staphylococcus aureus, an exotoxin producer 67

16.11 SCIENTIFIC DISCOVERY: Koch’s postulates are used to prove that a bacterium causes a disease
Koch’s postulates are four essential conditions used to establish that a certain bacterium is the cause of a disease. They are 1. find the bacterium in every case of the disease, 2. isolate the bacterium from a person who has the disease and grow it in pure culture, 3. show that the cultured bacterium causes the disease when transferred to a healthy subject, and 4. isolate the bacterium from the experimentally infected subject. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. Module describing the steps of Koch’s postulates and their utility today invites a discussion of scientific philosophy. Consider discussing with your class the use of the word proof. In particular, you might mention that science is never certain, although evidence can lead to conclusions reached with the highest levels of confidence. © 2012 Pearson Education, Inc. 68

16.11 SCIENTIFIC DISCOVERY: Koch’s postulates are used to prove that a bacterium causes a disease
Koch’s postulates were used to demonstrate that the bacterium Helicobacter pylori is the cause of most peptic ulcers. The 2005 Nobel Prize in Medicine was awarded to Barry Marshall and Robin Warren for this discovery. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. Module describing the steps of Koch’s postulates and their utility today invites a discussion of scientific philosophy. Consider discussing with your class the use of the word proof. In particular, you might mention that science is never certain, although evidence can lead to conclusions reached with the highest levels of confidence. © 2012 Pearson Education, Inc. 69

Figure 16.11 Figure Barry Marshall (left) and colleague Robin Warren 70

16.12 CONNECTION: Bacteria can be used as biological weapons
Bacteria that cause anthrax and the plague can be used as biological weapons. Bacillus anthracis killed five people in the United States in 2001. Yersinia pestis bacteria are typically carried by rodents and transmitted by fleas, causing the plague and can cause a pneumonic form of plague if inhaled. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. The many aspects of bacterial toxins often provoke student interest and can provide a rich opportunity for further student investigation. Consider having students prepare short reports on a toxin of their choice as a required or extra credit assignment. 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. © 2012 Pearson Education, Inc. 71

Figure 16.12 Figure Swellings (buboes) characteristic of the bubonic form of plague 72

16.12 CONNECTION: Bacteria can be used as biological weapons
Clostridium botulinum produces the exotoxin botulinum, the deadliest poison on earth. Botulinum blocks transmission of nerve signals and prevents muscle contraction. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Much of this chapter describes the traits and habits of single-celled prokaryotes and single-celled eukaryotes. Students might benefit by developing a series of tables that allow them to quickly review the properties of various groups, organized by size, shape, cell wall structure, surface modifications, and/or mode of nutrition. Students might easily be led to 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 new prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination. 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. The many aspects of bacterial toxins often provoke student interest and can provide a rich opportunity for further student investigation. Consider having students prepare short reports on a toxin of their choice as a required or extra credit assignment. 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. © 2012 Pearson Education, Inc. 73

16.13 Protists are an extremely diverse assortment of eukaryotes
Protists are a diverse collection of mostly unicellular eukaryotes, may constitute multiple kingdoms within the Eukarya, and refer to eukaryotes that are not plants, animals, or fungi. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 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. Teaching Tips The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is ever 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. © 2012 Pearson Education, Inc. 75

Protists obtain their nutrition in many ways. Protists include autotrophs, called algae, producing their food by photosynthesis, heterotrophs, called protozoans, eating bacteria and other protists, heterotrophs, called parasites, deriving their nutrition from a living host, and mixotrophs, using photosynthesis and heterotrophy. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 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. Teaching Tips The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is ever 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. © 2012 Pearson Education, Inc. 76

Autotrophy Heterotrophy Mixotrophy Caulerpa, a green alga
Figure 16.13A Autotrophy Heterotrophy Mixotrophy Figure 16.13A Protist modes of nutrition Caulerpa, a green alga Giardia, a parasite Euglena 77

Autotrophy Caulerpa, a green alga Figure 16.13A_1
Figure 16.13A_1 Protist modes of nutrition: Caulerpa, a green alga (part 1) Caulerpa, a green alga 78

Heterotrophy Giardia, a parasite Figure 16.13A_2
Figure 16.13A_2 Protist modes of nutrition: Giardia, a parasite (part 2) Giardia, a parasite 79

Mixotrophy Euglena Figure 16.13A_3
Figure 16.13A_3 Protist modes of nutrition: Euglena (part 3) Euglena 80

Protists are found in many habitats including anywhere there is moisture and the bodies of host organisms. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 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. Teaching Tips The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is ever 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. © 2012 Pearson Education, Inc. 81

Figure 16.13B Figure 16.13B A protist from a termite gut covered by thousands of flagella, viewed with scanning electron microscope (left) and light microscope (below). 82

Figure 16.13B_1 Figure 16.13B_1 A protist from a termite gut covered by thousands of flagella: SEM (part 1) 83

Figure 16.13B_2 Figure 16.13B_2 A protist from a termite gut covered by thousands of flagella: LM (part 2) 84

Recent molecular and cellular studies indicate that nutritional modes used to categorize protists do not reflect natural clades. Protist phylogeny remains unclear. One hypothesis, used here, proposes five monophyletic supergroups. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 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. Teaching Tips The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is ever 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. © 2012 Pearson Education, Inc. 85

16.14 EVOLUTION CONNECTION: Secondary endosymbiosis is the key to much of protist diversity
The endosymbiont theory explains the origin of mitochondria and chloroplasts. Eukaryotic cells evolved when prokaryotes established residence within other, larger prokaryotes. This theory is supported by present-day mitochondria and chloroplasts that have structural and molecular similarities to prokaryotic cells and replicate and use their own DNA, separate from the nuclear DNA of the cell. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 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 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. The endosymbiont theory for the origin of mitochondria and chloroplasts is also discussed in detail in Module Consider assigning this module in addition to chapter 16. Figure is especially useful for distinguishing between primary and secondary endosymbiosis and explaining the origin of some protist diversity. © 2012 Pearson Education, Inc. 86

Primary endosymbiosis Cyanobacterium Heterotrophic eukaryote
Figure 16.14_s1 Primary endosymbiosis Evolved into chloroplast Cyanobacterium 2 1 Nucleus Heterotrophic eukaryote Figure 16.14_s1 The theory of the origin of protistan diversity through endosymbiosis (step 1) 87

Primary endosymbiosis Green alga Chloroplast Evolved into chloroplast
Figure 16.14_s2 Primary endosymbiosis Green alga Chloroplast Evolved into chloroplast Cyanobacterium 2 3 Autotrophic eukaryotes 1 Nucleus Heterotrophic eukaryote Figure 16.14_s2 The theory of the origin of protistan diversity through endosymbiosis (step 2) Chloroplast Red alga 88

Primary endosymbiosis Green alga Chloroplast Evolved into chloroplast
Figure 16.14_s3 Primary endosymbiosis Green alga Chloroplast Evolved into chloroplast Cyanobacterium 2 3 Autotrophic eukaryotes 4 Heterotrophic eukaryotes 1 Nucleus Heterotrophic eukaryote Figure 16.14_s3 The theory of the origin of protistan diversity through endosymbiosis (step 3) Chloroplast Red alga 89

16.14 EVOLUTION CONNECTION: Secondary endosymbiosis is the key to much of protist diversity
Secondary endosymbiosis is the process in which an autotrophic eukaryotic protist became endosymbiotic in a heterotrophic eukaryotic protist and key to protist diversity. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. 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 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. The endosymbiont theory for the origin of mitochondria and chloroplasts is also discussed in detail in Module Consider assigning this module in addition to chapter 16. Figure is especially useful for distinguishing between primary and secondary endosymbiosis and explaining the origin of some protist diversity. © 2012 Pearson Education, Inc. 90

Primary endosymbiosis Secondary endosymbiosis Green alga Chloroplast
Figure 16.14_s4 Primary endosymbiosis Secondary endosymbiosis Green alga Chloroplast Evolved into chloroplast Cyanobacterium 2 3 Autotrophic eukaryotes 4 Heterotrophic eukaryotes 5 1 Nucleus Heterotrophic eukaryote Figure 16.14_s4 The theory of the origin of protistan diversity through endosymbiosis (step 4) Chloroplast Red alga 91

Primary endosymbiosis Secondary endosymbiosis Green alga Remnant of
Figure 16.14_s5 Primary endosymbiosis Secondary endosymbiosis Green alga Remnant of green alga Chloroplast Evolved into chloroplast Cyanobacterium Euglena 2 3 Autotrophic eukaryotes 4 Heterotrophic eukaryotes 5 1 Nucleus Heterotrophic eukaryote Figure 16.14_s5 The theory of the origin of protistan diversity through endosymbiosis (step 5) Chloroplast Red alga 92

16.15 Chromalveolates represent the range of protist diversity
Chromalveolates include diatoms, unicellular algae with a glass cell wall containing silica, Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 93

Figure 16.15A Figure 16.15A Diatom, a unicellular alga 94

Chromalveolates include diatoms, unicellular algae with a glass cell wall containing silica, dinoflagellates, unicellular autotrophs, heterotrophs, and mixotrophs that are common components of marine plankton, Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 95

Figure 16.15B Figure 16.15B A red tide caused by Gymnodinium, a dinoflagellate 96

Chromalveolates include diatoms, unicellular algae with a glass cell wall containing silica, dinoflagellates, unicellular autotrophs, heterotrophs, and mixotrophs that are common components of marine plankton, brown algae, large, multicellular autotrophs, Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 97

Figure 16.15C Figure 16.15C Brown algae: a kelp “forest” 98

Chromalveolates include diatoms, unicellular algae with a glass cell wall containing silica, dinoflagellates, unicellular autotrophs, heterotrophs, and mixotrophs that are common components of marine plankton, brown algae, large, multicellular autotrophs, water molds, unicellular heterotrophs, Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 99

Figure 16.15D Figure 16.15D Water mold (white threads) decomposing a goldfish 100

Chromalveolates include diatoms, unicellular algae with a glass cell wall containing silica, dinoflagellates, unicellular autotrophs, heterotrophs, and mixotrophs that are common components of marine plankton, brown algae, large, multicellular autotrophs, water molds, unicellular heterotrophs, ciliates, unicellular heterotrophs and mixotrophs that use cilia to move and feed, Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 101

Figure 16.15E Mouth Figure 16.15E A freshwater ciliate showing cilia distributed over the cell surface and around the mouth 102

Chromalveolates include diatoms, unicellular algae with a glass cell wall containing silica, dinoflagellates, unicellular autotrophs, heterotrophs, and mixotrophs that are common components of marine plankton, brown algae, large, multicellular autotrophs, water molds, unicellular heterotrophs, ciliates, unicellular heterotrophs and mixotrophs that use cilia to move and feed, and a group including parasites, such as Plasmodium, which causes malaria. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 103

16.16 CONNECTION: Can algae provide a renewable source of energy?
Fossil fuels are the organic remains of organisms that lived hundreds of millions of years ago and primarily consist of diatoms and primitive plants. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Students may think that fossil fuels largely consist of decayed animals such as dinosaurs. However, as the authors note, diatoms and primitive plants are thought to be responsible for most fossil fuels. Teaching Tips This is a very exciting time for new scientists entering the field of renewable fuels. Module is an opportunity to illustrate to 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. © 2012 Pearson Education, Inc. 104

16.16 CONNECTION: Can algae provide a renewable source of energy?
Lipid droplets in diatoms and other algae may serve as a renewable source of energy. If unicellular algae could be grown on a large scale, this oil could be harvested and processed into biodiesel. Numerous technical hurdles remain before industrial-scale production of biofuel from algae becomes a reality. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Students may think that fossil fuels largely consist of decayed animals such as dinosaurs. However, as the authors note, diatoms and primitive plants are thought to be responsible for most fossil fuels. Teaching Tips This is a very exciting time for new scientists entering the field of renewable fuels. Module is an opportunity to illustrate to 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. © 2012 Pearson Education, Inc. 105

Figure 16.16 Figure Green algae in a bioreactor 106

16.17 Rhizarians include a variety of amoebas
The two largest groups of Rhizaria are among the organisms referred to as amoebas. Amoebas move and feed by means of pseudopodia, temporary extensions of the cell. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 107

Foraminiferans are found in the oceans and in fresh water, have porous shells, called tests, composed of calcium carbonate, and have pseudopodia that function in feeding and locomotion. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 108

Figure 16.17A Figure 16.17A A foraminiferan (inset SEM shows a foram test) 109

Figure 16.17A_1 Figure 16.17A_1 A foraminiferan (part 1) 110

Figure 16.17A_2 Figure 16.17A_2 A foraminiferan: SEM of foram test (part 2) 111

Radiolarians are mostly marine and produce a mineralized internal skeleton made of silica. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 112

Figure 16.17B Figure 16.17B A radiolarian skeleton 113

16.18 Some excavates have modified mitochondria
Excavata has recently been proposed as a clade on the basis of molecular and morphological similarities. The name refers to an “excavated” feeding groove possessed by some members of the group. Excavates have modified mitochondria that lack functional electron transport chains and use anaerobic pathways such as glycolysis to extract energy. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 114

Excavates include heterotrophic termite endosymbionts Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 115

Figure 16.13B Figure 16.13B A protist from a termite gut covered by thousands of flagella, viewed with scanning electron microscope (left) and light microscope (below). 116

Excavates include heterotrophic termite endosymbionts, autotrophic species, mixotrophs such as Euglena Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 117

Mixotrophy Euglena Figure 16.13A_3
Figure 16.13A_3 Protist modes of nutrition: Euglena (part 3) Euglena 118

Excavates include heterotrophic termite endosymbionts, autotrophic species, mixotrophs such as Euglena, the common waterborne parasite Giardia intestinalis, Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 119

Autotrophy Heterotrophy Mixotrophy Caulerpa, a green alga
Figure 16.13A Autotrophy Heterotrophy Mixotrophy Figure 16.13A Protist modes of nutrition Caulerpa, a green alga Giardia, a parasite Euglena 120

Excavates include heterotrophic termite endosymbionts, autotrophic species, mixotrophs such as Euglena, the common waterborne parasite Giardia intestinalis, the parasite Trichomonas vaginalis, which causes 5 million new infections each year of human reproductive tracts, Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 121

Flagella Undulating membrane Figure 16.18A
Figure 16.18A A parasitic excavate: Trichomonas vaginalis Undulating membrane 122

Excavates include heterotrophic termite endosymbionts, autotrophic species, mixotrophs such as Euglena, the common waterborne parasite Giardia intestinalis, the parasite Trichomonas vaginalis, which causes 5 million new infections each year of human reproductive tracts, and the parasite Trypanosoma, which causes sleeping sickness in humans. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 123

Figure 16.18B Figure 16.18B A parasitic excavate: Trypanosoma (with blood cells) 124

16.19 Unikonts include protists that are closely related to fungi and animals
Unikonta is a controversial grouping joining amoebozoans and a group that includes animals and fungi, addressed at the end of this unit on protists. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 125

Amoebozoans have lobe-shaped pseudopodia and include many species of free-living amoebas, some parasitic amoebas, and slime molds. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 126

Figure 16.19A Figure 16.19A An amoeba beginning to ingest an algal cell 127

Plasmodial slime molds are common where there is moist, decaying organic matter and consist of a single, multinucleate mass of cytoplasm undivided by plasma membranes, called a plasmodium. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 128

Figure 16.19B Figure 16.19B A plasmodial slime mold: Physarum 129

Figure 16.19B_1 Figure 16.19B_1 A plasmodial slime mold: Physarum (part 1) 130

Figure 16.19B_2 Figure 16.19B_2 A plasmodial slime mold: Physarum (part 2) 131

Cellular slime molds are common on rotting logs and decaying organic matter and usually exist as solitary amoeboid cells, but when food is scarce, amoeboid cells swarm together, forming a slug-like aggregate that wanders around for a short time and then forms a stock supporting an asexual reproductive structure that produces spores. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 132

Figure 16.19C Figure 16.19C An aggregate of amoeboid cells (left) and the reproductive structure of a cellular slime mold, Dictyostelium 133

16.20 Archaeplastids include red algae, green algae, and land plants
Archaeplastids include: red algae, green algae, and land plants. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 134

Red algae are mostly multicellular, contribute to the structure of coral reefs, and are commercially valuable. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 135

Figure 16.20A Figure 16.20A An encrusted red alga on a coral reef 136

Green algae may be unicellular, colonial, or multicellular. Volvox is a colonial green algae, and Chlamydomonas is a unicellular alga propelled by two flagella. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 137

Volvox Chlamydomonas Figure 16.20B
Figure 16.20B Green algae, colonial (left) and unicellular (right) Volvox Chlamydomonas 138

Figure 16.20B_1 Figure 16.20B_1 Green algae, colonial: Volvox (part 1) Volvox 139

Chlamydomonas Figure 16.20B_2
Figure 16.20B_2 Green algae, unicellular: Chlamydomonas (part 2) Chlamydomonas 140

Ulva, or sea lettuce, is a multicellular green alga with a complex life cycle that includes an alternation of generations that consists of a multicellular diploid (2n) form, the sporophyte, that alternates with a multicellular haploid (1n) form, the gametophyte. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips Students can be encouraged to create their own table of traits, resembling Table 16.7 in organization, to distinguish between the groups addressed in Modules and 16.17– Alternately, you might create such a table to be completed by students while they study these modules. Beginning science students often need help learning how to organize information gained through reading and note taking. The great diversity of protists presents an opportunity for students to report on different types of protists and enhance their knowledge. For example, students can sketch their protist and identify reliable Web resources for additional details and clarity. You might collect and edit these Web references to serve as an aid for your entire class. These short exercises in content ownership allow students to develop a greater depth of understanding and increase interaction with the subject. © 2012 Pearson Education, Inc. 141

Mitosis Male gametophyte Spores Mitosis Gametes Female gametophyte Key
Figure 16.20C_s1 Mitosis Male gametophyte Spores Mitosis Gametes Female gametophyte Figure 16.20C_s1 The life cycle of Ulva, a multicellular green alga (step 1) Key Haploid (n) Diploid (2n) 142

Mitosis Male gametophyte Spores Mitosis Gametes Female gametophyte
Figure 16.20C_s2 Mitosis Male gametophyte Spores Mitosis Gametes Female gametophyte Fusion of gametes Figure 16.20C_s2 The life cycle of Ulva, a multicellular green alga (step 2) Zygote Key Haploid (n) Diploid (2n) 143

Mitosis Male gametophyte Spores Mitosis Gametes Female gametophyte
Figure 16.20C_s3 Mitosis Male gametophyte Spores Mitosis Gametes Female gametophyte Meiosis Fusion of gametes Figure 16.20C_s3 The life cycle of Ulva, a multicellular green alga (step 3) Sporophyte Zygote Mitosis Key Haploid (n) Diploid (2n) 144

Figure 16.20C_2 Figure 16.20C_2 The life cycle of Ulva, a multicellular green alga 145

16.21 EVOLUTION CONNECTION: Multicellularity evolved several times in eukaryotes
The origin of the eukaryotic cell led to an evolutionary radiation of new forms of life. Unicellular protists are much more diverse in form than simpler prokaryotes. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips The evolution of multicellularity requires the subdivision of labor in ways 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. Figure presents one potential scenario to account for the diversity of eukaryotes. It is a very helpful organizer for the textbook and discussions of these groups. © 2012 Pearson Education, Inc. 146

Multicellular organisms (seaweeds, plants, animals, and most fungi) are fundamentally different from unicellular organisms. A multicellular organism has various specialized cells that perform different functions and are interdependent. All of life’s activities occur within a single cell in unicellular organisms. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips The evolution of multicellularity requires the subdivision of labor in ways 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. Figure presents one potential scenario to account for the diversity of eukaryotes. It is a very helpful organizer for the textbook and discussions of these groups. © 2012 Pearson Education, Inc. 147

Multicellular organisms have evolved from three different lineages: brown algae evolved from chromalveolates, fungi and animals evolved from unikonts, and red algae and green algae evolved from achaeplastids. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips The evolution of multicellularity requires the subdivision of labor in ways 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. Figure presents one potential scenario to account for the diversity of eukaryotes. It is a very helpful organizer for the textbook and discussions of these groups. © 2012 Pearson Education, Inc. 148

Red algae Archaeplastids Other green algae Green algae Charophytes
Figure 16.21A Red algae Archaeplastids Other green algae Green algae Charophytes Land plants Ancestral eukaryote Amoebozoans Nucleariids Unikonts Fungi Figure 16.21A A hypothesis for the phylogeny of plants, fungi, and animals Choanoflagellates Key All unicellular Animals Both unicellular and multicellular All multicellular 149

One hypothesis states that two separate unikont lineages led to fungi and animals, diverging more than 1 billion years ago. A combination of morphological and molecular evidence suggests that choanoflagellates are the closest living protist relative of animals. Student Misconceptions and Concerns Students might think of evolution as a progression, with eukaryotes somehow fundamentally “better” than prokaryotes. As the authors note, however, eukaryotes cannot exist without prokaryotes, but prokaryotes can survive without eukaryotes. Teaching Tips The evolution of multicellularity requires the subdivision of labor in ways 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. Figure presents one potential scenario to account for the diversity of eukaryotes. It is a very helpful organizer for the textbook and discussions of these groups. © 2012 Pearson Education, Inc. 150

A nucleariid, closest living protistan relative of fungi Fungi
Figure 16.21B Nucleariids A nucleariid, closest living protistan relative of fungi Fungi 1 billion years ago Individual choanoflagellate Choanoflagellates Colonial choanoflagellate Figure 16.21B The closest living protist relatives of fungi (top) and animals (bottom) Sponge collar cell Animals Sponge 151

A nucleariid, closest living protistan relative of fungi Fungi
Figure 16.21B_1 Nucleariids A nucleariid, closest living protistan relative of fungi Figure 16.21B_1 The closest living protist relatives of fungi and animals (part 1) Fungi 152

Individual choanoflagellate Choanoflagellates Colonial
Figure 16.21B_2 Individual choanoflagellate Choanoflagellates Colonial choanoflagellate Sponge collar cell Animals Figure 16.21B_2 The closest living protist relatives of fungi and animals (part 2) Sponge 153

Figure 16.21B_3 Figure 16.21B_3 The closest living protist relative of fungi: a nucleariid (micrograph) 154

You should now be able to
Describe the structures and functions of the diverse features of prokaryotes; explain how these features have contributed to their success. Explain how populations of prokaryotes can adapt rapidly to changes in their environment. Describe the nutritional diversity of prokaryotes and explain the significance of biofilms. Explain how prokaryotes help clean up the environment. Compare the characteristics of the three domains of life; explain why biologists consider Archaea to be more closely related to Eukarya than to Bacteria. © 2012 Pearson Education, Inc. 155

Describe the diverse types of Archaea living in extreme and moderate environments. Distinguish between the subgroups of the domain Bacteria, noting the particular structure, special features, and habitats of each group. Distinguish between bacterial exotoxins and endotoxins, noting examples of each. Describe the steps of Koch’s postulates and explain why they are used. Explain how bacteria can be used as biological weapons. © 2012 Pearson Education, Inc. 156

Describe the extremely diverse assortment of eukaryotes. Explain how primary endosymbiosis and secondary endosymbiosis led to further cellular diversity. Describe the major protist clades noting characteristics and examples of each. Describe the life cycle of Ulva, noting each form in the alternation of generations and how each is produced. Explain how multicellular life may have evolved in eukaryotes. © 2012 Pearson Education, Inc. 157

Nutritional mode Energy source Carbon source Photoautotroph Sunlight
Figure 16.UN01 Nutritional mode Energy source Carbon source Photoautotroph Sunlight CO2 Chemoautotroph Inorganic chemicals Photoheterotroph Sunlight Organic compounds Chemoheterotroph Organic compounds Figure 16.UN01 Reviewing the Concepts, 16.4 158

negative plasma membrane
Figure 16.UN02 Exotoxin Secreted by cell Endotoxin Component of gram- negative plasma membrane Figure 16.UN02 Reviewing the Concepts, 16.10 Staphylococcus aureus Salmonella enteritidis 159

Staphylococcus aureus
Figure 16.UN02_1 Exotoxin Secreted by cell Figure 16.UN02_1 Reviewing the Concepts, (Staphylococcus aureus) Staphylococcus aureus 160

negative plasma membrane
Figure 16.UN02_2 Endotoxin Component of gram- negative plasma membrane Figure 16.UN02_2 Reviewing the Concepts, (Salmonella enteritidis) Salmonella enteritidis 161

(a) algae Green Ancestral eukaryote (c)
Figure 16.UN03 (a) Red algae algae Green Other green algae (b) Land plants Ancestral eukaryote (c) Amoebozoans Nucleariids Figure 16.UN03 Connecting the Concepts, question 2 (d) (e) (f) 162

Microbial Life: Prokaryotes and Protists

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