Ch 25 - The history of life on earth (1 slide per page)-2

2621 campbell reece 8th ed 28 fossil cyanobacteria

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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 layers • 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 can replicate...
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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.

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