1041SCG Lecture Notes - Lecture 8: Cambrian Explosion, Choanoflagellate, Microrna
28 Dec 2018
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Week 8 animal diversity and animal form and function. History: ancestor to all animals appeared about 770 million years ago. Were initially soft bodied but rapidly diversified during the cambrian explosion: sponges appeared 700 million years ago, cambrian explosion (530 million years ago) saw a huge increase in diversity. Fossils of 50% of extant animal phyla, especially bilaterians. Possible causes are: predation (arms race), increased atmospheric oxygen and development of hox genes and microrna: during palenzoic colonisation of land: Vertebrates and amniotes 365 million years ago: during mesozoic (250-65 mya) First small mammals: during cenozoic (65 mya) Max extinction: disappearance of large, non-flying dinosaurs and marine reptiles. All phyla are invertebrates except the chordate phylum which are vertebrates. Animal phylogeny: phylogenetic tree based on dna, morphology and body plan. Body plan is the set of morphological and developmental traits of living organisms. Body plans reflect evolution and can help build animal phylogenic tree.
