Evolution5 - Evolution #7: Early Earth, Continental Drift,...

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Evolution #7: Early Earth, Continental Drift, Early Life {RECALL: Phylogenies are based on common ancestries inferred from fossil, fossil record o sedimentary rocks are the richest source of fossils, but other mediums are used as well o fossil record is based on sequence in which fossils have accumulated in such strata o fossils inform phylogeny only if their age can be determined o fossil record is a substantial, but incomplete chronicle of evolutionary change o fossil record is biased in favor of abundant, long-lived, widespread species w/ hard shells, skeletons, or other parts that facilitated their fossilization o in general, organisms that share v similar morphologies or similar DNA sequences are likely to be more closely related than organisms w/ vastly diff structures or sequences o in some cases, the morphological divergence betwn related species can be Tree of Life: Intro to Biological Diversity: Changing Life on a Changing Earth Conditions on early Earth made the origin of life possible chemical & physical processes on early Earth, aided by the emerging force of selection, produced v simple cells thru sequence of 4 stages 1. abiotic synthesis of small organic molecules (aa, nucleotides) 2. joining of these small molecules into polymers (proteins, nucleic acids) 3. packaging of these materials into protobionts (droplets w/ membranes that maintained an internal chemistry diff from that of their surroundings) 4. origin of self-replicating molecules that eventually made inheritance possible these scenarios have many uncertainties but can be tested in lab synthesis of organic compounds on early earth o o 1 st few 00my: collisions & bombardments from space hindered origin of life, o 3.9bya: collision phase ended o 3.8bya: oldest rocks known (found in Greenland) o 1 st atm: thick w/ water vapor & compounds released by volcanic eruptions (N, CO2, CH4, NH3, H, HS) as earth cooled, water vapor condensed into o Miller-Urey expmt (developed from Oparin-Haldane hypothesis) yields amino
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Evolution5 - Evolution #7: Early Earth, Continental Drift,...

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