Lec13_ChangeStasis - The one and only illustration in On...

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The one and only illustration in On the Origin of Species (1859) “Transitional forms”: whales from ungulates… Is this a “finely graduated” organic chain of intermediates?
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In other words… The fossil record provides abundant examples of “transitional forms” but is ambiguous about the tempo and mode (i.e., the rate and pattern) of evolutionary change morphology time Depicting change through time: the “time-morphology diagram” 1 2 A B ± ± Anagenesis Cladogenesis (aka speciation) rate of anagenetic change from Moore, Lalicker, and Fischer (1953) Invertebrate fossils The “traditional” view of cladogenesis
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If most evolutionary change (even speciation) is in the anagenetic mode, then rates of evolution = rates of anagenesis Punctuated Equilibrium Eldredge & Gould (1972) The origins of Punctuated Equilibrium: The stages of (allopatric) speciation (Mayr, 1942) Ernst Mayr (1904-2005) Two modes of allopatric speciation
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Lec13_ChangeStasis - The one and only illustration in On...

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