L6 Macroevolution

L6 Macroevolution - BILD 3 July 2, 2010 Allopatric &...

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BILD 3 July 2, 2010 Woodruff: macroevolution 1 Allopatric & Sympatric Speciation • In allopatric speciation – A new species forms while geographically isolated from its parent population – Sometimes called geographic speciation • In sympatric speciation – The emergence of a reproductive barrier (e.g., chromosome doubling or niche shifts) isolates a subset of a population without geographic separation from the parent species – Sometimes called instantaneous speciation PROCESSES OF SPECIATION Responsible for today’s ~10 million species Process can be very fast: instantaneous in case of polyploidy 100’s of generations in lake cichlids Or very slow: 1000’s of generations of separation may be insufficient to lead to the evolution of reproductive isolation. Ultimately, species go extinct or are replaced by divergent daughter species. The fossil record is so full of gaps that the gaps are used to define paleontological species in the absence of biological data. Average duration of a species of mammal: ~1-2 my Oldest species: so called living fossils ANAGENESIS STASIS CLADOGENESIS PHYLETIC GRADUALISM PUNCTUATED EQUILIBRIUM MACROEVOLUTION AND ADAPTIVE RADIATION Classical explanation: The outcome of gradual microevolutionary changes - gradual allelic substitution and exclusive role of natural selection. Phyletic gradualism Evolution seldom reverses itself (Dolo’s law) to any significant extent because many genes are involved and most changes are deleterious. Therefore evolving taxa diverge from one another. ICONOGRAPHY OF THE BRANCHING BUSH CONES OF INCREASING COMPLEXITY Adaptive radiation and the exploitation of new environments Galapagos finches (1 species evolves into 13 in <5 My) Hawaiian honeycreepers (1 evolves into 14 in few My)
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This note was uploaded on 07/27/2010 for the course BIOLOGY BILD 3 taught by Professor Davidwoodruff during the Spring '10 term at San Diego.

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L6 Macroevolution - BILD 3 July 2, 2010 Allopatric &amp;...

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