ENV100Y5 Lecture Notes - Lecture 5: Chemotroph, Chemosynthesis, Panspermia
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ENV100Y5 Full Course Notes
Verified Note
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Document Summary
Several hypotheses have been proposed to explain life"s origin. Life comes into the picture and everything changes - heterotrophic hypothesis ( primordial soup") Life originated from inorganic chemicals in the ocean. First life forms used organic compounds for energy. Chemoautotrophic hypothesis (ocean depths fed by chemicals) Life originated at deep sea hydrothermal vents. Fossil remnant of long-dead organism, preserved in stone. Fossil record information about the history of past life. Species have come and gone, and new life forms have evolved in history of earth. Chemical evidence shows that life was here". Life played a central role in evolution of earths systems. Early life forms: chemosynthetic, thermophilic bacteria appeared by ~4 ga at latest. Photosynthetic cyanobacteria (blue-green-algae) appeared ~3. 9 ga at latest. Life had two main influences on the chemistry of the atmosphere. Life contributed to the buildup of oxygen in the atmosphere. Cyanobacteria use up co2 and emit o2. Free" oxygen in the atmosphere by ~2 ga ago.
