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Chapter 16

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  1. 0 Chapter 16 The Origin and Evolution of Microbial Life: Prokaryotes and Protists

  2. Colorized SEM 650 PROKARYOTES • 16.7 Prokaryotes have inhabited Earth for billions of years • Prokaryotes are the oldest life-forms • And remain the most numerous and widespread organisms Figure 16.7

  3. Three Domains – Archaea, Bacteria, Eukarya

  4. 16.8 Bacteria and archaea are the two main branches of prokaryotic evolution • Domains Bacteria and Archaea • Are distinguished on the basis of nucleotide sequences and other molecular and cellular features

  5. Differences between Bacteria and Archaea Table 16.8

  6. Colorized SEM 3,000 Colorized SEM 12,000 Colorized SEM 9,000 • 16.9 Prokaryotes come in a variety of shapes • Prokaryotes may be shaped as • Spheres (cocci) • Rods (bacilli) • Curves or spirals (vibrio or spirochaete) Figure 16.9A–C

  7. 16.10Various features contribute to the success of prokaryotes • External Structures • Cell wall • Pili • Flagella • Reproduction and adaptation • Specialized internal structures • Form colonies • Varied methods of obtaining food

  8. Colorized TEM 70,000  Capsule • External Structures • The cell wall • Is one of the most important features of nearly all prokaryotes • Is covered by a sticky capsule Figure 16.10A

  9. Pili Colorized TEM 16,000 • Some prokaryotes • Stick to their substrate with pili Figure 16.10B

  10. Flagellum Colorized TEM 14,000 Plasmamembrane Cell wall Rotary movement ofeach flagellum • Motility • Many bacteria and archaea • Are equipped with flagella, which enable them to move Figure 16.10C

  11. Reproduction and Adaptation • Prokaryotes • Have the potential to reproduce quickly in favorable environments

  12. Endospore TEM 34,000 • Some prokaryotes can withstand harsh conditions • By forming endospores Figure 16.10D

  13. Respiratorymembrane TEM 45,000 Thylakoidmembrane TEM 6,000 • Internal Organization • Some prokaryotic cells • Have specialized membranes that perform metabolic functions Figure 16.10E

  14. 16.11 Prokaryotes obtain nourishment in a variety of ways • As a group • Prokaryotes exhibit much more nutritional diversity than eukaryotes

  15. Types of Nutrition • Autotrophs make their own organic compounds from inorganic sources • Photoautotrophs harness sunlight for energy and use CO2 for carbon • Chemoautotrophs obtain energy from inorganic chemicals instead of sunlight

  16. Heterotrophs obtain their carbon atoms from organic compounds • Photoheterotrophs can obtain energy from sunlight • Chemoheterotrophs are so diverse that almost any organic molecule can serve as food for some species Figure 16.11A

  17. Nutritional classification of organisms Table 16.11

  18. Colorized SEM 13,000 • Metabolic Cooperation • In some prokaryotes • Metabolic cooperation occurs in surface-coating colonies called biofilms Figure 16.11B

  19. 16.12Archaea thrive in extreme environments (extremophiles) — and in other habitats • Archaea are common in • Salt lakes, acidic hot springs, deep-sea hydrothermal vents Figure 16.12A, B

  20. Plankton dispersal • Archaea are also a major life-form in the ocean Phytoplankton

  21. Colorized TEM 5,000 LM 13,000 • 16.13 Bacteria include a diverse assemblage of prokaryotes • Bacteria are currently organized into several subgroups, including • Proteobacteria • Chlamydias • Spirochetes Figure 16.13A, B

  22. Nitrogen-fixingcells Colorized SEM 2,8000 Colorized SEM 2,800 LM 650 Photosyntheticcells • Gram-positive bacteria • Cyanobacteria, which photosynthesize in a plantlike way Figure 16.13C, D

  23. Tick that carriesthe Lyme diseasebacterium SEM 2,800 Spirochetethat causesLyme disease SEM 12,000 “Bull’s-eye”rash CONNECTION • 16.14 Some bacteria cause disease • Pathogenic bacteria cause disease by producing • Exotoxins or endotoxins Figure 16.14A, B

  24. CONNECTION • 16.15 Bacteria can be used as biological weapons • Bacteria, such as the species that causes anthrax • Can be used as biological weapons Figure 16.15

  25. CONNECTION • 16.16 Prokaryotes help recycle chemicals and clean up the environment • Bioremediation • Is the use of organisms to clean up pollution

  26. Rotatingspray arm Rock bed coated withaerobicbacteriaand fungi Outflow Liquid wastes • Prokaryotes are decomposers in • Sewage treatment and can clean up oil spills and toxic mine wastes Figure 16.16A, B

  27. PROTISTS • 16.17The eukaryotic cell probably originated as a community of prokaryotes • Eukaryotic cells • Evolved from prokaryotic cells more than 2 billion years ago

  28. The nucleus and endomembrane system • Probably evolved from infoldings of the plasma membrane • Mitochondria and chloroplasts • Probably evolved from aerobic and photosynthetic endosymbionts, respectively

  29. Cytoplasm Plasmamembrane Endoplasmicreticulum Nuclearenvelope Ancestral prokaryote Nucleus Membrane infolding Aerobic heterotrophicprokaryote Cell with nucleus andendomembrane system Somecells Photosyntheticprokaryote Ancestral host cell Endosymbiosis Mitochondrion Chloroplast Mitochondrion Photosyntheticeukaryotic cell Endosymbiotic Theory • A model of the origin of eukaryotes Figure 16.17

  30. LM 275 • 16.18Protists are an extremely diverse assortment of eukaryotes • Protists • Are mostly unicellular eukaryotes • Molecular systematics • Is exploring eukaryotic phylogeny Figure 16.18

  31. Fungi Ciliates Plants Diatoms Animals Amoebas Red algae Water molds Green algae Diplomonads Brown algae Apicomplexans Euglenozoans Dinoflagellates Choanoflagellates Cellular slime molds Plasmodial slime molds Closest algal relatives of plants Amoebozoa Alveolates Stramenopila Ancestral eukaryote How are Protists classified? • 16.19 A tentative phylogeny of eukaryotes includes multiple clades of protists • The taxonomy of protists • Is a work in progress Figure 16.19

  32. Colorized SEM 4,000 • 16.20Diplomonads and euglenozoans include some flagellated parasites • The parasitic Giardia • Is a diplomonad with highly reduced mitochondria Figure 16.20A

  33. Colorized SEM 1,300 Colorized SEM 1,300 • Euglenozoans • Include trypanosomes and Euglena Figure 16.20B, C

  34. SEM 2,300 • 16.21Alveolates have sacs beneath the plasma membrane and include dinoflagellates, apicomplexans, and ciliates • Dinoflagellates • Are unicellular algae Figure 16.21A

  35. TEM 26,000 Apex Red blood cell • Apicomplexans are parasites • Such as Plasmodium, which causes malaria Figure 16.21B

  36. Cilia Macronucleus LM 60 • Cilliates • Use cilia to move and feed Figure 16.21C

  37. 16.22Stramenopiles are named for their “hairy” flagella and include the water molds, diatoms, and brown algae • This clade includes • Fungus-like water molds Figure 16.22A

  38. LM 400 • Photosynthetic, unicellular diatoms Figure 16.22B

  39. Brown algae, large complex seaweeds Figure 16.22C

  40. LM 185 • 16.23Amoebozoans have pseudopodia and include amoebas and slime molds • Amoebas • Move and feed by means of pseudopodia Figure 16.23A

  41. A plasmodial slime mold is a multinucleate plasmodium • That forms reproductive structures under adverse conditions Figure 16.23B

  42. 45 Slug-like aggregate LM 1,000 Amoeboid cells Reproductivestructure 15 • Cellular slime molds • Have unicellular and multicellular stages Figure 16.23C

  43. 16.24 Red algae and green algae are the closest relatives of land plants • Red algae • Contribute to coral reefs Figure 16.24A

  44. Chlamydomonas Volvox colonies LM 1,200 LM 80 • Green algae • May be unicellular, colonial, or multicellular Figure 16.24B

  45. Mitosis Malegametophyte Spores Gametes Mitosis Femalegametophyte Meiosis Fusion ofgametes Sporophyte Zygote Key Mitosis Haploid (n) Diploid (2n) • The life cycles of many algae • Involve the alternation of haploid gametophyte and diploid sporophyte generations Figure 16.24C

  46. Gamete Locomotorcells Somatic cells 2 3 1 Food-synthesizingcells Unicellular protist Colony Early multicellular organismwith specialized, interdepen-dent cells Later organism thatproduces gametes • 16.25Multicellularity evolved several times in eukaryotes • Multicellularity evolved in several different lineages • Probably by specialization of the cells of colonial protists Figure 16.25

  47. Multicellular life arose over a billion years ago