W10_103_9a_PCLife

W10_103_9a_PCLife - Life in the Precambrian Prelude to Us...

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Life in the Precambrian Prelude to Us 1. Origins Stromatolites - Life’s most successful form
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First Evidence for Life Beginning of the Archean • Chemical (3.5-3.8 Byrs) • Fossils (3.2-3.5 Byrs) Evidence? Isua Supergroup Oldest Evidence for Life: Isua Supergroup Greenland (3.8 Gyrs)
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12 C/ 13 C Enrichment in Organics 7‰ 12 C Depleted (less 12 C than atm) 18‰ 12 C Enriched (more 12 C than atm) 25±10‰ 12 C Difference CO 2 in Atmosphere (includes 12 CO 2 and 13 CO 2 ) Carbon Isotopic Composition Limestone and Organic Carbon 0 1 2 3 4 Age (billion years ago) 0 -25 ± 13 C (‰) -50 +25 Higher 12 C Lower 12 C ? 3.8 Byr = Greenland
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Oldest Fossils: Apex Chert Fossils (3.5 Gyr) Conditions for Life 1. Organic compounds 2. Energy 3. Water 4. Stability
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Where Requirements for Life Present on the Hadean Earth? 1. Organic Compounds - Yes 2. Energy - Yes - Sunlight & High Geothermal 3. Water - Not stable 4. Stability - No Verdict - Life possible but unlikely to “survive” 2004 - Fred Sulahria Where Requirements for Life Present on the Archean Earth? 1. Organic Compounds - Yes 2. Energy - Yes - Sunlight & High Geothermal 3. Water - Yes 4. Stability - Yes Verdict - Yes - Conditions are right on! First evidence may be Early Archean (3.8 Byrs)
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What is Life? • Composed of organic compounds • Resistance to entropy (disorder) – Requires energy (must be able to gather and process (metabolize) energy) • Ability to maintain a controlled environment – Requires ability to be isolated from environment • Information storage • Self replication – Including ability to pass on information • Ability to adapt to its environment Inorganic to Organic Hurdles • Inorganic production of organic compounds (amino acids, nucleotides,
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This note was uploaded on 01/11/2012 for the course GEO 103 taught by Professor Robviens during the Winter '10 term at Bellevue College.

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W10_103_9a_PCLife - Life in the Precambrian Prelude to Us...

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