BIO 200 Lecture Notes - Lecture 35: Cambrian Explosion, Continental Drift, Citric Acid Cycle
3 Jun 2019
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Document Summary
Eukaryotic life appeared in the fossil record ~2. 5 bya. Since the first organisms (prokaryotic cells) originated >4. 3 bya, this means it had taken ~2 billion years for the first complex cells to evolve. And since the first multicellular organisms appear as fossils perhaps 1. 5 bya, it took about a billion years for true multicellularity to evolve. The first animal fossils are recorded at 700 in the. 100 million years later there was a spectacular world-wide appearance of most modern animal phyla (cambrian. Explosion) which fossilize well because they have skeletons. Major events in the history of earth: hadean eon 4. 6!3. 8 bya. Earth & moon formed as solid bodies: archean eon 3. 8!2. 6 bya. Animal kingdom: organisms that are eukaryotic multicellular: heterotrophic feed by ingestion. The phylogenetic relationships shown below is largely based on dna evidence because the fossil evidence is too poor to show the details.
