BIO SCI 97 Chapter Notes -Cambrian Explosion, Multicellular Organism, Cyanobacteria
30 Jan 2014
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Same 4 mechanisms, over geologic time scale: estimates of age of earth/solar system. Current estimate: 4. 5 bya: oceans formed by 3. 8 bya, no o2, much solar radiation, life 3. 6 to 3. 8 bya. Fossils were seen through thin film of sediments: abiotic synthesis of organic molecules, molecules join to form macromolecules, molecules packaged into protobionts, origin of self-replicating molecules. 4 eons 3 = precambrian : last eon = last 0. 5 billion years 3 eras. Eras represent distinct age in history of earth and its life. Most history of higher organisms in last eon. The first 4 billion years on earth origin of 3 domains. Oxygen revolution: evolution of photosynthesis 2. 8 bya (primitive cyanobacteria) 1. 5 bya levels high enough for aerobic eukaryotes. First eukaryotes evolve by endosymbiosis (2. 1 bya) nucleus, organelles. Severe ice ages limited size and diversity. Many phyla of living animals suddenly appear in fossil record.
