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Life Sciences
Luc Bernier

January 16 , 2013 Life Sci 2H03: Environmental Life Sciences Early Life Geological Time Scale - Hadean: time from the formation of the Solar System and early accretion of the planet - To the origin of life - Archaean: time of the beginning of life - Followed by Proterozoic - Phanerozoic since then The Prebiotic Hadean Environment - from creation of Solar System: 4.6 Gyr - planetisimul to planets - earth received finite amounts of water vapour and carbon: determined during these early stages - CO 2n Earth: tied up in carbonate rocks - E.g. limestone - Water: liquid and mainly found in oceans, 90%, Venus closer to sun has a more powerful greenhouse affect due to CO , too h2t for water to remain liquid Early Earth - lot of volcanic activity - influenced by gases - impact with meteorites causing to lose gases to surroundings - earth’s ocean would evaporate many times and condense again - eventually temperatures cooled down Earth’s Early Atmosphere - early atmosphere – overall reducing environment: hydrogen(H ), methane2 (CH 4, ammonia (NH ), w4ter, nitrogen (N ), no 2elease of oxygen due to photosynthesis. Small amounts of carbon dioxide/monoxide and hydrogen sulfide - today’s atmosphere – overall oxidizing environment: nitrogen (N ), oxygen2 (O 2, carbon dioxide (CO ),2water (H O) 2 - happened over geological time scales The Miller-Urey Experiment - because of the reducing composition, with the combination of electrical energy could have lead to the formation simple organic compounds - based on Oparin-Haldane hypothesis: life would have arisen from chemical reactions in Earth’s atmosphere The RNA World - earliest forms of life where RNA - organisms would have been entirely based on RNA - capable of self-replication and enzymatic activity - ribozymes: able to cleave RNA - carry information and able to carry out enzymatic activity: development of proteins The Faint Young Sun - 4.4 to 4.0 Gyr: early Sun was fainter by a quarter to a third than it is now - wasn’t emitting as much energy as it is now producing - would have lead to desert environments and glaciation - how would life have emerged under these conditions? Survival Strategies in Glacial Environments - fundamental prerequisite for life to exist in polar climates: ab
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