ASTRO-110 Lecture Notes - Lecture 13: Hadean, Cyanobacteria, Hydrogen Sulfide
9 Sep 2020
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Simple organisms with a few enzymes and rudimentary metabolism resembling the simplest modern bacteria and archaea, no nucleus. Photosynthesis and ability to digest other organisms must have arrived later. Modern parallels are archaea in hot sulphur springs. With limited sets of enzymes, early dna replication was buggy: E. g. , photosynthesis is a complex metabolic process, yet already suggested in stromatolites and microfossils 3. 5 byr ago. Photosynthesis process also likely evolved: first with development of light-absorbing pigments then with utilization of a variety of products: e. g. , hydrogen sulphide (h2s), rather than water (h2o) Oxygen build-up: from photosynthetic organisms 2. 5 0. 5 byr ago. Animals characterized by their body plans or phyla. Mammals and reptiles are of the phylum chordata : with internal skeletons. All 30 phyla arise during a period of only 40 myr: Is the only major diversification of phyla in the geological record. Oxygen reached a critical level for survival of larger life-forms.
