chapter 6 - 1 Origin and Evolution of The Cell Biological...

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Unformatted text preview: 1 Origin and Evolution of The Cell Biological and geologic history are closely intertwined Fossilized mats of prokaryotes 2.5 billion years old mark a time when photosynthetic How Ancient Cells Changed the Planet time when photosynthetic bacteria were producing O 2 that made the atmosphere aerobic These fossilized mats are called stromatolites (=bedrock) Planet Earth formed some 4.6 billion years ago Life began on a young Earth EARLY EARTH AND THE ORIGIN OF LIFE The early atmosphere contained H 2 O , CO , CO 2 , N 2 , and possibly some CH 4 , but little or no free O 2 Volcanic activity , lightning , and UV radiation were intense Fossilized prokaryotes date back 3.5 billion years Pre Cambrian bedrock Life may have developed from nonliving materials as = 500 million years ago Earliest animals ; diverse algae Earliest multicellular eukaryotes ? Earliest eukaryotes ars ago early as 3.9 billion years ago Accumulation of atmospheric O 2 from photosynthetic cyanobacteria Oldest known prokaryotic fossils Origin of life ? Formation of Earth Billions of yea 2 Small organic molecules must have appeared first This probably happened when How did life originate? This probably happened when inorganic chemicals were energized by heat , lightning or UV radiation Stanley Millers fantastic experiment 1953: Millers Hi : amino acids and organic molecules could have been generated on a lifeless Earth Water vapor CH 4 Electrode Condenser Cold The Primitive Atmosphere: H, CH4, NH3, H2O lightning Stanley Millers experiment Cold water Cooled water containing organic compounds amino acids, sugars, nucleotide bases Sample for chemical analysis H 2 O Warm water: primitive sea H 2 O CH 4 NH 3 H 2 H 2 O amino acids, sugars, nucleotide bases Glucose Nucleotide bases Sugar-phosphate backbone 3 end 5 end Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a The DNA double helix new strand 5 end New strands 3 end 5 end 3 end 5 end 3 Large molecules could have polymerized on hot rocks or clay originating polypeptides and short nucleic acids Where did the first polymers originate?Where did the first polymers originate?...
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chapter 6 - 1 Origin and Evolution of The Cell Biological...

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