© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Chapter 15 The Evolution of Microbial Life

© 2010 Pearson Education, Inc. MAJOR EPISODES IN THE HISTORY OF LIFE Earth was formed about 4.6 billion years ago. Prokaryotes –Evolved by 3.5 billion years ago –Began oxygen production about 2.7 billion years ago –Lived alone for almost 2 billion years –Continue in great abundance today

© 2010 Pearson Education, Inc. Single-celled eukaryotes first evolved about 2.1 billion years ago. Multicellular eukaryotes first evolved at least 1.2 billion years ago.

Precambrian Common ancestor to all present-day life Origin of Earth Earth cool enough for crust to solidify Oldest prokaryotic fossils Atmospheric oxygen begins to appear due to photosynthetic prokaryotes Millions of years ago 4,5004,0003,5003,0002,500 Figure 15.1a

PaleozoicMesozoicCenozoic Bacteria Archaea Plants Fungi Animals Prokaryotes Eukaryotes Protists Oldest eukaryotic fossils Origin of multicellular organisms Oldest animal fossils Plants and symbiotic fungi colonize land Extinction of dinosaurs First humans Millions of years ago Cambrian explosion 2,0001,5001, Figure 15.1b

© 2010 Pearson Education, Inc. All the major phyla of animals evolved by the end of the Cambrian explosion, which began about 540 million years ago and lasted about 10 million years. Plants and fungi –First colonized land about 500 million years –Were followed by amphibians that evolved from fish

Humans Origin of solar system and Earth Pre sent Animals Coloniz of land ation Multi eukar cellular yotes Sing eukar cel yotes le- led Atmo oxy sphe ric gen Bil ars ons of ago ye li kary otes Pro Figure 15.2 What if we use a clock analogy to tick down all of the major events in the history of life on Earth?

© 2010 Pearson Education, Inc. Resolving the Biogenesis Paradox All life today arises by the reproduction of preexisting life, or biogenesis. If this is true, how could the first organisms arise? From the time of the ancient Greeks until well into the 19 th century, it was commonly believed that life regularly arises from nonliving matter, an idea called spontaneous generation. Remember “Cell Theory” ?

© 2010 Pearson Education, Inc. Today, most biologists think it is possible that life on early Earth produced simple cells by chemical and physical processes.

Figure 15.3

© 2010 Pearson Education, Inc. Hypothesis for the Origin of Life According to one hypothesis, the first organisms were products of chemical evolution in four stages. Abiogenesis

The Process of Science: Can Biological Monomers Form Spontaneously? Observation: Modern biological macromolecules are all composed of elements that were present in abundance on the early Earth. Question: Could biological molecules arise spontaneously under conditions like those on the early Earth? Inorganic Organic ? © 2010 Pearson Education, Inc.

Hypothesis: A closed system designed in the laboratory to simulate early Earth conditions could produce biologically important organic molecules from inorganic ingredients. Prediction: Organic molecules would form and accumulate.

© 2010 Pearson Education, Inc. Experiment: An apparatus was built to mimic the early Earth atmosphere and included –Hydrogen gas (H 2 ), methane (CH 4 ), ammonia (NH 3 ), and water vapor (H 2 O) –Sparks, discharged into the chamber to mimic the prevalent lightning of the early Earth –A condenser to cool the atmosphere, causing water and dissolved compounds to “rain” into the miniature “sea”

Stanley Miller re-creating his 1953 experiment Miller and Urey’s experiment “Sea” H2OH2O Sample for chemical analysis Cooled water containing organic molecules Cold water Condenser Electrode “Atmosphere” Water vapor CH 4 NH 3 H2H2 Figure 15.4

© 2010 Pearson Education, Inc. Results: After the apparatus had run for a week, an abundance of organic molecules essential for life had collected in the “sea,” including amino acids, the monomers of proteins. Since Miller and Urey’s experiments, laboratory analogues of the primeval Earth have produced –All 20 amino acids –Several sugars

© 2010 Pearson Education, Inc. From Chemical Evolution to Darwinian Evolution Over millions of years –Natural selection favored the most efficient pre-cells –The first prokaryotic cells evolved

© 2010 Pearson Education, Inc. PROKARYOTES…..They’re Everywhere! Prokaryotes lived and evolved all alone on Earth for 2 billion years before eukaryotes evolved. Prokaryotes –Are found wherever there is life –Far outnumber eukaryotes –Can cause disease –Can be beneficial –Typically much smaller

© 2010 Pearson Education, Inc. Prokaryotes live deep within the Earth and in habitats too cold, too hot, too salty, too acidic, or too alkaline for any eukaryote to survive.

Figure 15.6

Plasma membrane (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA) Pili (attachment structures) Colorized TEM Figure 4.4

Cytoskeleton RibosomesCentriole Lysosome Flagellum Nucleus Plasma membrane Mitochondrion Rough endoplasmic reticulum (ER) Golgi apparatus Smooth endoplasmic reticulum (ER) Idealized animal cell Idealized plant cell Cytoskeleton Mitochondrion Nucleus Rough endoplasmic reticulum (ER) Ribosomes Smooth endoplasmic reticulum (ER) Golgi apparatus Plasma membrane Channels between cells Not in most plant cells Central vacuole Cell wall Chloroplast Not in animal cells Figure 4.5 Animal Cell Plant Cell

SHAPES OF PROKARYOTIC CELLS Spherical (cocci)Rod-shaped (bacilli)Spiral Colorized SEM Colorized TEM Figure 15.8

© 2010 Pearson Education, Inc. About half of all prokaryotes are mobile, using flagella. Many have one or more flagella that propel the cells away from unfavorable places or toward more favorable places, such as nutrient-rich locales.

MODES OF NUTRITION LightChemical Chemoautotrophs Photoautotrophs Photoheterotrophs Chemoheterotrophs Energy source Elodea, an aquatic plant Rhodopseudomonas Little Owl (Athene noctua) Bacteria from a hot spring Organic compounds Carbon source CO 2 Colorized TEM Figure 15.12

The Two Main Branches of Prokaryotic Evolution: Bacteria and Archaea By comparing diverse prokaryotes at the molecular level, biologists have identified two major branches of prokaryotic evolution: –Bacteria –Archaea (more closely related to eukaryotes) © 2010 Pearson Education, Inc.

Bacteria That Cause Disease Bacteria and other organisms that cause disease are called pathogens. Most pathogenic bacteria produce poisons. –Exotoxins are poisonous proteins secreted by bacterial cells. –Endotoxins are not cell secretions but instead chemical components of the outer membrane of certain bacteria.

Haemophilus influenzae Cells of nasal lining Colorized SEM Figure 15.14

© 2010 Pearson Education, Inc. The best defenses against bacterial disease are –Sanitation –Antibiotics –Education

© 2010 Pearson Education, Inc. Lyme disease is –Caused by bacteria carried by ticks –Treated with antibiotics, if detected early

“Bull’s-eye” rash Tick that carries the Lyme disease bacterium Spirochete that causes Lyme disease SEM Figure 15.15

© 2010 Pearson Education, Inc. Bioterrorism Humans have a long and ugly history of using organisms as weapons. –During the Middle Ages, armies hurled the bodies of plague victims into enemy ranks. –Early conquerors, settlers, and warring armies in South and North America gave native peoples items purposely contaminated with infectious bacteria. –In 1984, members of a cult in Oregon contaminated restaurant salad bars with Salmonella bacteria. –In the fall of 2001, five Americans died from the disease anthrax in a presumed terrorist attack.

Figure 15.16

© 2010 Pearson Education, Inc. The Ecological Impact of Prokaryotes Pathogenic bacteria are in the minority among prokaryotes. Far more common are species that are essential to our well-being, either directly or indirectly.

© 2010 Pearson Education, Inc. Prokaryotes and Chemical Recycling Prokaryotes play essential roles in –Chemical cycles in the environment –The breakdown of organic wastes and dead organisms

© 2010 Pearson Education, Inc. Prokaryotes and Bioremediation Bioremediation is the use of organisms to remove pollutants from –Water –Air –Soil A familiar example is the use of prokaryotic decomposers in sewage treatment.

Liquid wastes Outflow Rotating spray arm Rock bed coated with aerobic prokaryotes and fungi Figure 15.17

© 2010 Pearson Education, Inc. Certain bacteria –Can decompose petroleum –Are useful in cleaning up oil spills

Bacteria Archaea Prokaryotes Eukarya Protists Plants Fungi Animals Figure 15.UN02

© 2010 Pearson Education, Inc. PROTISTS Protists –Are eukaryotic –Evolved from prokaryotic ancestors –Are ancestral to all other eukaryotes, which are –Plants –Fungi –Animals

© 2010 Pearson Education, Inc. The Origin of Eukaryotic Cells Eukaryotic cells evolved by –The infolding of the plasma membrane of a prokaryotic cell to form the endomembrane system and –Endosymbiosis, one species living inside another host species, in which free-living bacteria came to reside inside a host cell, producing mitochondria and chloroplasts

(a) Origin of the endomembrane system(b) Origin of mitochondria and chloroplasts Plasma membrane Ancestral prokaryote DNA Cytoplasm Endoplasmic reticulum Membrane infolding Nucleus Nuclear envelope Cell with nucleus and endomembrane system Photosynthetic eukaryotic cell Photosynthetic prokaryote Aerobic heterotrophic prokaryote Endosymbiosis (Some cells) Mitochondrion Chloroplast Figure 15.20

© 2010 Pearson Education, Inc. The Diversity of Protists Protists can be –Unicellular –Multicellular More than any other group, protists vary in –Structure –Function

© 2010 Pearson Education, Inc. The classification of protists remains a work in progress. The four major categories of protists, grouped by lifestyle, are –Protozoans –Slime molds –Unicellular algae –Seaweeds

© 2010 Pearson Education, Inc. Protozoans Protists that live primarily by ingesting food are called protozoans. Protozoans with flagella are called flagellates and are typically free-living, but sometimes are nasty parasites.

A flagellate: Giardia A foram An apicomplexan A ciliate An amoeba Another flagellate: trypanosomes Food being ingested Pseudopodium of amoeba Red blood cell LM TEM LM Colorized SEM Apical complex Cilia Oral groove Figure 15.21

© 2010 Pearson Education, Inc. Unicellular and Colonial Algae Algae are –Photosynthetic protists –Found in plankton, the communities of mostly microscopic organisms that drift or swim weakly in aquatic environments

© 2010 Pearson Education, Inc. Unicellular algae include –Diatoms, which have glassy cell walls containing silica –Dinoflagellates, with two beating flagella and external plates made of cellulose

© 2010 Pearson Education, Inc. Green algae are –Unicellular –Sometimes flagellated, such as Chlamydomonas –Colonial, sometimes forming a hollow ball of flagellated cells, as seen in Volvox

(a) A dinoflagellate, with its wall of protective plates (c) Chlamydomonas, a unicellular green alga with a pair of flagella (b) A sample of diverse diatoms, which have glossy walls (d) Volvox, a colonial green alga Colorized SEM SEM LM Figure 15.24

© 2010 Pearson Education, Inc. Seaweeds –Are only similar to plants because of convergent evolution –Are large, multicellular marine algae –Grow on or near rocky shores –Are often edible

© 2010 Pearson Education, Inc. Seaweeds are classified into three different groups, based partly on the types of pigments present in their chloroplasts: –Green algae –Red algae –Brown algae (including kelp)

Green algaeRed algaeBrown algae Figure 15.25

Evolution Connection: The Origin of Multicellular Life Multicellular organisms have interdependent, specialized cells that perform different functions, such as feeding, waste disposal, gas exchange, and protection—and are dependent on each other. © 2010 Pearson Education, Inc.

Unicellular protist Colony Locomotor cells Food-synthesizing cells Early multicellular organism with specialized, interdependent cells Later organism with gametes and somatic cells Somatic cells Gamete Figure