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Unformatted text preview: . 26.21 (Campbell & Reece 8th Ed.) 28 Fossil Cyanobacteria
• Common in fossil record from ~3.5 BYA
• Morphology of modern forms very similar
Found in stromatolites:
• Thin films of sediment
bind to cyanobacteria –
forming thin mineralized
• Found today in shallow,
salty tropical bays
e.g. Shark Bay, Australia 29
29 Key Events:
2. Origin of life
When did life begin? Prokaryotes were only
organisms on earth
from ~3.5 to 2 BYA. Figure 26.10 (Campbell 7th ed) 30 2. Origin of life How did life begin?
Proposed 4 step scenario to produce a basic cell: 1 Abiotic synthesis of small organic molecules Test: construct early earth
atmosphere, add energy
Results: Formation of
• amino acids
• other organic compounds
Conclusion: abiotic synthesis
of organic molecules is possible
1953, Stanley Miller, Chicago
Figure 4.2 (Campbell 8th ed) 31
Proposed 4 step scenario to produce a basic cell: 2 Joining of small organic molecules into macromolecules Experiment: Drip amino acid monomer solutions onto clay
Result: Amino acid polymers formed spontaneously
Conclusion: Polymers can be formed w/o the use of enzymes
(Clay mineral lattice structure provided template for organic matter organization) 32
Proposed 4 step scenario to produce a basic cell: 3 Polymers & monomers packed into membrane bound
“protocell” droplets that maintain an internal environment.
Question: How might a membrane bound protocell have formed?
Test: Phospholipids in H2O - spontaneously form protocells (aka liposome)
w/ selectively permeable membranes! Membrane 33
Proposed 4 step scenario to produce a basic cell: 4 Self replication Protocells
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This note was uploaded on 02/12/2014 for the course BIOLOGY 2011 taught by Professor Woo during the Fall '10 term at University of Central Florida.
- Fall '10