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And related algae alive today can be used to study

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Unformatted text preview: – Hollow sphere of colonial flagellates Trichoplax adherens –  (BioEssays 2005 – 27:1294 ­1302) Volvox spp. and related algae alive today can be used to study the evolu?on of mul?cellularity http://vimeo.com/26514497 2 4/12/13 Paleozoic Life – Cambrian Explosion ~543 MYA, Start of Paleozoic Era (Cambrian Period) Diversifica?on of metazoans Oxygen approaches modern levels Cambrian Explosion – Almost all modern phyla & classes of skeletonized marine animals •  Also many groups of ex?nct phyla and classes •  Fossils  ­ appear very suddenly; Within about 30 MY, as liale as 5 to 10 MY •  Wray et al (1996) – Molecular clock, 1000 Mya? •  •  •  •  First appearance marine classes •  Frequencies of first appearances of classes of marine animal fossils. (From Erwin, Valen?ne and Sepkoski 1987) •  V=Vendian; Cm=Cambrian; O=Ordovician; S=Silurian; D=Devonian; C=Carboniferous; P=Permian; Tr=Triassic; J=Jurassic; K=Cretaceous; T=Ter?ary 3 4/12/13 Burgess Shale Fauna 505 mya 140 species of animals in 119 genera represented Charles Walcott Burgess Shale Fauna •  Pikaia (Early Chordate) •  Fundamental Body Plan – notochord and muscle bands •  Wh...
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