GSC 111 Lecture 11: Chapter 11 Origins of Life
26 Nov 2017
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4. 6 bya (formation of earth) to 5. 4 bya (cambrian explosion) Why the sun gets brighter with time. Hydrogen fuses to form helium with time. More energy is produced and thus more energy needs to be emitted. Luminosity= energy we absorb from the sun. Assume same atm= temps would be -25 degrees celsius. From a theoretical standpoint- early earth appears to have been warm because of early sun. Evidence for life beginning in 3. 8 ga. Oxygen and hydrogen isotopes suggest warmer seawater temperatures. *co2 and methane kept early earth warm. Sequence dna to define relatedness and evolutionary rate. Methanogenesis may have originated as early as 4. 1-3. 8 bya. Older the rock, the greater the chance that it no longer exists. Around 3 billion years- geologic record becomes scant. Bracketed by volcanic deposits that can be radiometrically dated. Randomly scattered like raisins in raisin bread. Cell width of 11 species= 2 bacteria, 3 prokaryotes, 6 cyanobacteria.
