Evolution 6a

Evolution 6a - Main models of speciation 1 Another view of...

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1 Main models of speciation
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2 Another view of the four… Darwin’s brilliant insight… Even the origin of new species begins with inter-individual variation Tempo and Mode in Evolution
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3 In gradualism, the assumed mechanism is allopatric speciation. Gaps in the record reflect imperfect fossilization
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4 But phyletic gradualism is only ONE way to go from A to B… or A to C. Can also Can also get there by repeated episodes of rapid speciation!
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5 In punctuated equilibrium, the assumed mechanism is peripatric speciation “Williamson’s Molluscs” (Tanzania) Each evolving line: long periods of stasis Change occurs at speciation ONLY
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6 213 144 MYA Ammonoids: cephalopod Mollusks (now extinct) Niles Eldredge 2005 408 248 360 286 Gaps in the record are not a problem of fossilization, They’re part of the DATA! (Transitional forms are relatively few and ephemeral)
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7 Cladogenesis Two components to evolution Anagenesis What causes the overall trend?
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Evolution 6a - Main models of speciation 1 Another view of...

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