Astronomy 2021A/B Chapter Notes - Chapter 6: Eukaryote, Archaea, Stromatolite
12 Dec 2014
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Document Summary
3 lines of fossil evidence point to idea that life arose quite early: i) stromatolites rocks characterized by distinctive layered structure ancient stromatolites look similar to mats formed today by living stromatolites living ones contain layers of sediment mixed w/ diff microbes those on top gain energy through photosynthesis beneath use org. compounds layered structure caused by migration upward some controversy about biological origin b/c sedimentation can mimic layering scientists have confidence of existence as far back as 3. 5 billion years ago if we are correct about photosynthetic life existing 3. 5 billion years ago, can infer primitive life existed earlier, ii) microfossils finding microfossils tough b/c rocks become rare and altered w/ age greatest controversy over oldest microfossil of 3. 5 billion years found that rock formed near deep sea vent therefore cannot be photosynthetic b/c sunlight does not penetrate to deep sea.
