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
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.
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 SelfReplicating Molecules
– Stage 4: Formation of Pre-Cells
The Primordial Soup
Figure 15.4b
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.
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
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
Hydrothermal Vent
– Methanogens inhabit the bottoms of lakes and swamps.
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)
The Structure, Function, and Reproduction of Prokaryotes
• Some prokaryotes are large, can
perform photosynthesis, or can
form colonies
• 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.
Cyanobacteria)
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
Four Modes of Nutrition Seen in Prokaryotes
Includes photosynthetic
cyanobacteria like
Oscillatoria
Table 15.1
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!
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
Industrial Applications of Bacterial Growth in Society
Using bacteria to decompose human sewage
Using bacteria to break down oil after an oilspill
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
Eukaryotes Evolved From Prokaryotes
Figure 15.18
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
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
• 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)
– Ciliates move by means of
cilia (e.g. Paramecium,
Vorticella)
Euglena Motion
Amoeba Pseudopodia
Vorticella Cilia
Paramecium Cilia
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
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)
Volvox Colony
• 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
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