The Origin and Evolution of Microbial Life: Prokaryotes and Protists
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Transcript of The Origin and Evolution of Microbial Life: Prokaryotes and Protists
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The Origin and Evolution of Microbial Life: Prokaryotes and
Protists
Chapter 16
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How Ancient Bacteria Changed the World Mounds of rock found near the Bahamas Contain photosynthetic prokaryotes
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Stromatolites in northern Canada
Figure 16.0Ax1
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Fossilized mats 2.5 billion years old mark a time when photosynthetic prokaryotes Were producing enough O2 to make the atmosphere
aerobic
Layers of a bacterial mat
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Bacterial mats
Figure 16.0Ax2
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EARLY EARTH AND THE ORIGIN OF LIFE The early atmosphere probably contained
H2O, CO, CO2, N2, PO43- and some CH4
Volcanic activity, lightning, and UV radiation were intense
Figure 16.1A
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A clock analogy tracks the origin of the Earth to the present day And shows some major events in the history
of Earth and its life
PaleozoicMeso-
zoic
Ceno-zoic
Humans
Land plants
Animals
Multicellulareukaryotes
Single-celledeukaryotes
Origin of solarsystem andEarth
1
2
4
3
Proterozoiceon
Archaeaneon
Billions of years ago
Atmospheric oxygen
Prokaryotes
Figure 16.1C
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16.2 How did life originate? Organic molecules May have been formed abiotically in the conditions on
early Earth
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Miller – Urey Experiment Simulations of such conditions
Have produced amino acids, sugars, lipids, and the nitrogenous bases found in DNA and RNA
Cooled watercontaining organic molecules
Cold water
Condenser
Sample forchemical analysis
H2O“Sea”
Water vapor“Atmosphere”
Electrode
CH4
NH3 H 2
Figure 16.3B
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16.4 The first polymers may have formed on hot rocks or clay
Organic polymers such as proteins and nucleic acids
May have polymerized on hot rocks
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Fig. 19.6, p. 297
membrane-bound proto-cells livingcells
self-replicating system enclosed in aselectively permeable, protective lipid sphere
DNA RNA enzymes andother proteins
formation ofprotein–RNA systems,
evolution of DNA
formation oflipid spheres
spontaneous formation of lipids,carbohydrates, amino acids, proteins,nucleotides under abiotic conditions
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16.6 Membrane-enclosed molecular co-ops may have preceded the first cells
RNA might have acted as templates for the formation of polypeptides
Which in turn assisted in RNA replication
Self-replication of RNA
Self-replicating RNA acts astemplate on which poly-peptide forms.
Polypeptide acts as primitiveenzyme that aids RNAreplication.
RNA
Polypeptide
Figure 16.6A
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Fig. 19.11, p. 301
DNA
infolding of plasma membrane
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Membranes may have separated various aggregates of self-replicating molecules Which could be acted on by natural selection
LM 6
50
Membrane
Polypeptide
RNA
Figure 16.6B, C
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Fossilized prokaryote and a living bacterium
Figure 16.1Dx1
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Origin of Life
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Origin of LifeHydrothermal Vent Life
http://www.youtube.com/watch?v=4LoiInUoRMQ
How Did Life Originate?http://www.youtube.com/watch?v=ozbFerzjkz4
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Fig. 19.7a, p. 298-9
chemical and molecular evolution, first into self-replicating systems, then into membranesof proto-cells by 3.8 billion years ago.
In a second majordivergence, theancestors of archaebacteriaand of eukaryoticcells start downtheir separateevolutionaryroads.
The first majordivergencegives rise toeubacteria andto the commonancestor ofarchaebacteriaand eukaryoticcells.
Hydrogen-Rich, Anaerobic Atmosphere Oxygen in Atmosphere: 10%
3.8 billionyears ago
3.2 billionyears ago
2.5 billionyears ago
The amount of genetic informationincreases; cell size increases; thecytomembrane system and thenuclear envelope evolve throughmodification of cell membranes.
Cyclic pathway ofphotosynthesisevolves in someanaerobic bacteria.
Noncyclic pathwayof photosynthesis(oxygen-producing)evolves in somebacterial lineages.
Aerobic respiration evolvesin many bacterial groups.
ORIGIN OFPROKARYOTES
EUBACTERIALLINEAGE
ANCESTORS OFEUKARYOTES
ARCHAEBACTERIALLINEAGE
ARCHAEBACTERIAExtreme halophiles
Methanogens
Extreme thermophiles
EUKARYOTESHeterotrophic protistans
EUBACTERIAOxygen-producing photosynthetic eubacteria (e.g., cyanobacteria)Other photosynthetic eubacteria
Heterotrophic and chemoautotropic eubacteria
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Fig. 19.7b, p. 298-9
(The ozone layer gradually develops) 20%
ORIGINS OF EUKARYOTESthe first protistans
ORIGINS OF ANIMALS
ORIGINS OF FUNGI
ORIGINS OF PLANTS
origin of mitosis, meiosis
ENDOSYMBIOTIC ORIGINS OF MITOCHONDRIA
ENDOSYMBIOTIC ORIGINS OF CHLOROPLASTS Oxygen-producing photosynthetic
eubacterium and early eukaryote become symbionts.
Aerobic species becomes endosymbiont of anaerobic forerunner of eukaryotess.
1.2 billionyears ago
900 millionyears ago
435 millionyears ago
present
ARCHAEBACTERIAExtreme halophiles
Methanogens
Extreme thermophiles
EUKARYOTESAnimals
Heterotrophic protistans
Fungi
Photosynthetic protistans
Plants
EUBACTERIAOxygen-producing photosynthetic eubacteria (e.g., cyanobacteria)
Other photosynthetic eubacteria
Heterotrophic and chemoautotropic eubacteria