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CHAPTER 16 The Origin and Evolution of Microbial Life: Prokaryotes and Protists

CHAPTER 16 The Origin and Evolution of Microbial Life: Prokaryotes and Protists. Modules 16.7 – 16.12. PROKARYOTES…The first true cells…. Prokaryotes have inhabited Earth for at least 3.5 billion years. Prokaryotes are the oldest life-forms. They lack a nucleus and membrane bound organelles.

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CHAPTER 16 The Origin and Evolution of Microbial Life: Prokaryotes and Protists

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  1. CHAPTER 16The Origin and Evolution of Microbial Life: Prokaryotes and Protists Modules 16.7 – 16.12

  2. PROKARYOTES…The first true cells… Prokaryotes have inhabited Earth for at least 3.5 billion years • Prokaryotes are the oldest life-forms. They lack a nucleus and membrane bound organelles. • They remain the most numerous and widespread organisms on Earth today • Some live in environments that are similar to the conditions on early earth. They include oxygen free depths of the Black Sea, boiling waters of hot springs, and deep sea vents. • Today there are two Divisions of prokaryotes, Archea and Bacteria. Figure 16.7

  3. Archaea—the extremophiles • Sheltered from evolutionary alteration, the Archea are relics of the first stages of life on earth. • The first to be studied were the methanogens, who are only able to grow in the absence of oxygen. They convert CO2 and H2 into methane gas(CH4). • Some live in salty environments like the Dead Sea (halophiles) and others live in deep sea vents and are extreme thermophiles (185F and 245x pressure at sea level). • Their DNA holds genes which are unlike any known to molecular biologists. Utilizing a molecular clock, it is hypothesized that the second group of prokaryotes, Bacteria, diverged from Archea approximately 3.5 billion years ago.

  4. Bacteria and Archaea Table 16.8

  5. 16.9 All Prokaryotes come in a variety of shapes • Spheres (cocci) are the most common • Rods (bacilli) • Curves or spirals Figure 16.9A-C

  6. 16.10 Prokaryotes obtain nourishment in a variety of ways • These E. Coli colonies are growing with only glucose as an organic nutrient Figure 16.10

  7. Photoautotrophs and chemoautotrophs • Heterotrophs obtain carbon from organic compounds • Photo-heterotrophs and chemo-heterotrophs • Autotrophs obtain carbon from CO2 and are of two types Table 16.10

  8. They may have gotten their energy from sulfur and iron compounds • The first cells were most likely chemoautotrophs

  9. 16.11 Archaea thrive in extreme environments—and in the ocean • Archaea live in • anaerobic swamps • salt lakes • acidic hot springs • deep-sea hydrothermal vents • animal digestive systems Figure 16.11A, B

  10. 16.12 Diverse structural features help prokaryotes thrive almost everywhere • Rotating flagella aid in locomotion Flagellum Plasmamembrane Cell wall Rotary movements ofeach flagellum Figure 16.12A

  11. Pili help cells cling to surfaces Pili Figure 16.12B

  12. Endospores allow certain bacteria to survive environmental extremes in a resting stage Endospore Figure 16.12C

  13. Many prokaryotes grow in linear filaments Figure 16.12D

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