The Evolution of Microbial Life CHAPTER 15

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The Evolution of Microbial Life CHAPTER 15

• Milestones in the Evolution of Life
• The Ubiquity of Microbes
• Prokaryotes
• Two Domains Eubacteria vs Archaeans
• Shape, Metabolism, and Reproduction
• Nutritional Modes
• Ecological Impact
• Development of Eukaryotic Life
• Protist Diversity
• Animal-like Protists Protozoans
• Plant-like Protists Unicellular and
  Multicellular Algae

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Major Episodes in the History of Life

• Prokaryotes appeared about 3.5 billion years ago.
• Oxygen production began about 2.5 billion years
  ago.
• Single-celled eukaryotic organisms evolved about
  2.2 billion years ago.

• Multicellular eukaryotes evolved about 1 billion
  years ago.
• All the major phyla of animals evolved by the end
  of the Cambrian explosion, which began about 540
  million years ago.
• About 475 million years ago
• Plants and fungi colonized land.
• Amphibians evolved from fish, and vertebrate life
  moved onto land.

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The Origin of Life and the First Cells

• Most biologists now think it is possible that
  chemical and physical processes on the early
  Earth produced simple cells.

• Stage 1 Abiotic Synthesis of Organic Monomers

• Stage 2 Abiotic Synthesis of Polymers

• Stage 3 Origin of Self-Replicating Molecules

• Stage 4 Formation of Pre-Cells

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The Primordial Soup
Figure 15.4b
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Enclosed Structures Pre-Cells?
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From Chemical Evolution to Darwinian Evolution

• Over millions of years,
• Natural selection favored the most efficient
  pre-cells.
• The first prokaryotic cells evolved.

• Prokaryotes
• Lived and evolved all alone on Earth for 2
  billion years.

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The Evolution of Microbial Life CHAPTER 15

• Milestones in the Evolution of Life
• The Ubiquity of Microbes
• Prokaryotes
• Two Domains Eubacteria vs Archaeans
• Shape, Metabolism, and Reproduction
• Nutritional Modes
• Ecological Impact
• Development of Eukaryotic Life
• Protist Diversity
• Animal-like Protists Protozoans
• Plant-like Protists Unicellular and
  Multicellular Algae

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Characteristics of Prokaryotes

• Theyre everywhere!
• Prokaryotes far outnumber the eukaryotes and are
  found in soil, water, air, and inside other
  living things
• Most are beneficial or neutral to humans, a small
  percentage cause disease

• The majority of known prokaryotes belong to
  Domain Eubacteria

• The Archaeans (Domain Archaea) are often
  extremophiles
• Halophiles thrive in salty environments.
• Extreme thermophiles live in hot springs or vents
• Methanogens inhabit the bottoms of lakes and
  swamps.

Hydrothermal Vent
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The Structure, Function, and Reproduction of
Prokaryotes

• Prokaryotic cells
• Lack true nuclei, membrane-enclosed organelles,
  and have cell walls of murein or pseudomurein

• Prokaryotes come in several shapes
• Spherical (cocci)
• Rod-shaped (bacilli)
• Spiral (spirochetes)

• Most prokaryotes are unicellular and very small
  (1-10 um)

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The Structure, Function, and Reproduction of
Prokaryotes

• Some prokaryotes are large, can perform
  photosynthesis, or can form colonies

Cyanobacteria)

• About half of all prokaryotes can move by means
  of one or more flagella

• Some prokaryotes form endospores that can survive
  harsh conditions (chemicals radiation)

• Most prokaryotes can reproduce by binary fission
  at very high rates if conditions are favorable.

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The Evolution of Microbial Life CHAPTER 15

• Milestones in the Evolution of Life
• The Ubiquity of Microbes
• Prokaryotes
• Two Domains Eubacteria vs Archaeans
• Shape, Metabolism, and Reproduction
• Nutritional Modes
• Ecological Impact
• Development of Eukaryotic Life
• Protist Diversity
• Animal-like Protists Protozoans
• Plant-like Protists Unicellular and
  Multicellular Algae

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Four Modes of Nutrition Seen in Prokaryotes
Includes photosynthetic cyanobacteria like
Oscillatoria
Table 15.1
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Some Bacteria Are Pathogenic (Disease-Causing)

• Bacteria are successful when invading host
  organisms by producing poisonous exotoxin
  proteins or containing endotoxins within their
  cells walls

• Examples of human bacterial diseases include Lyme
  Disease, tuberculosis, botulism, tetanus,
  gangrene, shigellosis, and strep throat

• The best defenses against bacterial disease are
  sanitation, antibiotics, and education.

• Using antibacterial products everywhere in the
  home is not the answer!

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Prokaryotes Have a Huge Ecological Impact

• Prokaryotes are essential to chemical cycling and
  decomposition of dead organisms
• Without prokaryotes, new life would not be
  possible

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Industrial Applications of Bacterial Growth in
Society
Using bacteria to decompose human sewage
Using bacteria to break down oil after an oilspill
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The Evolution of Microbial Life CHAPTER 15

• Milestones in the Evolution of Life
• The Ubiquity of Microbes
• Prokaryotes
• Two Domains Eubacteria vs Archaeans
• Shape, Metabolism, and Reproduction
• Nutritional Modes
• Ecological Impact
• Development of Eukaryotic Life
• Protist Diversity
• Animal-like Protists Protozoans
• Plant-like Protists Unicellular and
  Multicellular Algae

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Eukaryotes Evolved From Prokaryotes
Figure 15.18
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The Evolution of Microbial Life CHAPTER 15

• Milestones in the Evolution of Life
• The Ubiquity of Microbes
• Prokaryotes
• Two Domains Eubacteria vs Archaeans
• Shape, Metabolism, and Reproduction
• Nutritional Modes
• Ecological Impact
• Development of Eukaryotic Life
• Protist Diversity
• Animal-like Protists Protozoans
• Plant-like Protists Unicellular and
  Multicellular Algae

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Protists (Kingdom Protista)

• Protists
• Are eukaryotic
• Mostly unicellar but some multicellular
• Categorized by nutritional modes
• Animal-like protists called protozoans ingest
  food
• Plant-like protists called algae use sunlight

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Protozoans

• Protozoans (Animal-like protists) categorized by
  how they move

• Flagellates move by means of flagella (e.g.
  trypanosomes)

Euglena Motion

• Amoebas move by means of pseudopodia (e.g.
  foraminifera and radiolarians in ocean plankton)

Amoeba Pseudopodia

• Ciliates move by means of cilia (e.g. Paramecium,
  Vorticella)

Vorticella Cilia
Paramecium Cilia
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The Evolution of Microbial Life CHAPTER 15

• Milestones in the Evolution of Life
• The Ubiquity of Microbes
• Prokaryotes
• Two Domains Eubacteria vs Archaeans
• Shape, Metabolism, and Reproduction
• Nutritional Modes
• Ecological Impact
• Development of Eukaryotic Life
• Protist Diversity
• Animal-like Protists Protozoans
• Plant-like Protists Unicellular and
  Multicellular Algae

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Algae

• Algae (Plant-like Protists)
• Subdivided into unicellular and multicellular

• Unicellular algaes (often found in plankton)
• Diatoms
• Dinoflagellates
• Colonial Algae (e.g. Volvox)

• Multicellular algae (seaweeds)
• Large, multicellular, marine
• Classified by photosynthetic pigments green,
  red, brown

Volvox Colony
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Biology and Society Bioterrorism

• During the fall of 2001, five Americans died from
  the disease anthrax in a presumed terrorist
  attack.
• Microbes can be used as weapons

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The Evolution of Microbial Life CHAPTER 15

• Milestones in the Evolution of Life
• The Ubiquity of Microbes
• Prokaryotes
• Two Domains Eubacteria vs Archaeans
• Shape, Metabolism, and Reproduction
• Nutritional Modes
• Ecological Impact
• Development of Eukaryotic Life
• Protist Diversity
• Animal-like Protists Protozoans
• Plant-like Protists Unicellular and
  Multicellular Algae