The Evolution of Microbial Life CHAPTER 15 Milestones in the Evolution of Life The Ubiquity of Microbes Prokaryotes Two Domains: Eubacteria vs Archaeans

The Evolution of Microbial Life

CHAPTER 15


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

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.

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

The Origin of Life and the First 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

Figure 15.4b

The Primordial Soup

Enclosed Structures – Pre-Cells?

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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•Prokaryotes









Characteristics of Prokaryotes

• They’re 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

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)

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

The Structure, Function, and Reproduction of Prokaryotes

• 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)

Cyanobacteria)

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


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•Prokaryotes









Table 15.1

Four Modes of Nutrition Seen in Prokaryotes

Includes photosynthetic cyanobacteria like Oscillatoria

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

Some Bacteria Are Pathogenic (Disease-Causing)

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

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

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

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

Using bacteria to decompose human sewage

Using bacteria to break down oil after an oilspill

Industrial Applications of Bacterial Growth in Society


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•Prokaryotes









Figure 15.18

Eukaryotes Evolved From Prokaryotes


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•Prokaryotes









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

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

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

– 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)

Euglena Motion

Paramecium Cilia

Vorticella Cilia

Protozoans


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•Prokaryotes









Algae

• Algae (Plant-like Protists)

– Subdivided into unicellular and multicellular

Volvox Colony

– 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

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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•Prokaryotes









Documents

The Evolution of Microbial Life CHAPTER 15 Milestones in the Evolution of Life The Ubiquity of Microbes Prokaryotes Two Domains: Eubacteria vs Archaeans