Disruptive Selection

Disruptive Selection - A species can be defined as one or...

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Disruptive Selection Disruptive selection favors individuals at both extremes of variation: selection is against the middle of the curve. This causes a discontinuity of the variations, causing two or more morphs or distinct phenotypes. The African swallowtail butterfly ( Papilo dardanus ) produces two distinct morphs, both of which resemble brightly colored but distasteful butterflies of other species. Each morph gains protection from predation although it is in fact quite edible. Speciation As populations diverge, they form similar but related species. When are two populations new species? When populations no longer interbreed they are thought to be separate species. As natural selection adapts populations occupying different environments, they will diverge into races, subspecies, and finally separate species.
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Unformatted text preview: A species can be defined as one or more populations of interbreeding organisms that are reproductively isolated in nature from all other organisms. Genetic divergence results when adaptation, drift and mutation act on populations. Barriers to gene flow between populations isolate those populations, ultimately leading to the formation of new and separate species. Allopatric Speciation Populations begin to diverge when gene flow between them is restricted. Geographic isolation is often the first step in allopatric speciation. Other mechanisms may develop that further restrict reproduction between populations: these are the reproductive isolating mechanisms....
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This note was uploaded on 11/29/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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