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

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 Colorized SEM 650  Figure 16.7

Three Domains – Archaea, Bacteria, Eukarya

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

Differences between Bacteria and Archaea Table 16.8

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

16.10 Various 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

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

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

Motility Many bacteria and archaea Are equipped with flagella, which enable them to move Flagellum Plasma membrane Cell wall Rotary movement of each flagellum Colorized TEM 14,000 Figure 16.10C

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

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

Internal Organization Some prokaryotic cells Have specialized membranes that perform metabolic functions Respiratory membrane Thylakoid membrane TEM 45,000 TEM 6,000 Figure 16.10E

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

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

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

Nutritional classification of organisms Table 16.11

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

Salt lakes, acidic hot springs, deep-sea hydrothermal vents 16.12 Archaea 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

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

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

Gram-positive bacteria Cyanobacteria, which photosynthesize in a plantlike way Colorized SEM 2,800 LM 650  Photosynthetic cells Nitrogen-fixing cells Colorized SEM 2,8000  Figure 16.13C, D

CONNECTION 16.14 Some bacteria cause disease Pathogenic bacteria cause disease by producing Exotoxins or endotoxins SEM 12,000  Spirochete that causes Lyme disease “Bull’s-eye”rash Tick that carries the Lyme disease bacterium SEM 2,800 Figure 16.14A, B

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

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

Prokaryotes are decomposers in Sewage treatment and can clean up oil spills and toxic mine wastes Liquid wastes Outflow Rotating spray arm Rock bed coated with aerobic bacteria and fungi Figure 16.16A, B

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

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

Endosymbiotic Theory A model of the origin of eukaryotes Figure 16.17 Cytoplasm Ancestral prokaryote Plasma membrane Endoplasmic reticulum Nucleus Nuclear envelope Cell with nucleus and endomembrane system Membrane infolding Aerobic heterotrophic prokaryote Ancestral host cell Endosymbiosis Mitochondrion Chloroplast Photosynthetic eukaryotic cell Photosynthetic prokaryote Some cells A model of the origin of eukaryotes Figure 16.17

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

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 Diplomonads Euglenozoans Dinoflagellates Apicomplexans Ciliates Water molds Diatoms Brown algae Amoebas Plasmodial slime molds Cellular slime molds Fungi Choanoflagellates Animals Red algae Green algae Closest algal relatives of plants Plants Alveolates Stramenopila Amoebozoa Ancestral eukaryote Figure 16.19

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

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

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

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

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

Fungus-like water molds 16.22 Stramenopiles 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

Photosynthetic, unicellular diatoms LM 400 Figure 16.22B

Brown algae, large complex seaweeds Figure 16.22C

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

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

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

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

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

The life cycles of many algae Involve the alternation of haploid gametophyte and diploid sporophyte generations Mitosis Male gametophyte Gametes Spores Meiosis Fusion of gametes Female gametophyte Zygote Sporophyte Haploid (n) Diploid (2n) Key Figure 16.24C

16.25 Multicellularity evolved several times in eukaryotes Multicellularity evolved in several different lineages Probably by specialization of the cells of colonial protists Unicellular protist Colony Early multicellular organism with specialized, interdepen- dent cells Later organism that produces gametes Food- synthesizing cells Locomotor cells Somatic cells Gamete 1 2 3 Figure 16.25

Multicellular life arose over a billion years ago