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13 Cards in this Set
- Front
- Back
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Define Allopatric
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Allopatric
Species live in different geographic regions |
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Define Sympatric
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Sympatric
Species live in the same geographic region |
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What does allopatric do?
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pop physically isolated
by geographic barrier • little/no gene flow |
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Allopatric Main Model for
Speciation 2 |
1. geographic isolation
•little or no gene flow between populations. 2. genetic divergence •Two isolated populations will evolve independently (microevolution). – Natural selection and/or genetic drift |
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Geographical Isolation
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Geographical Isolation
• some sort of barrier prevents gene flow between populations of a species. – mountains, rivers, oceans, highways, plate tectonics. • Given enough time, reproductive isolation can evolve – speciation |
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Reproductive Isolation
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Reproductive Isolation
-genetic divergence can result in reproductive barriers. - Reproductive barriers “allow” sympatry and thus “allow” dispersal outside |
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Reproductive Isolation mechanisms
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mechanical, temporal, behavioral,Ecological Isolation
– Two populations prefer different habitats. • Gamete Mortality • Postzygotic isolation – Sterile hybrids… |
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sympatric speciation
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sympatric speciation
• NO geographic separation • but reproductive isolation occurs anyway |
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Gradualist Model
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Gradualist Model
• Populations evolve differences gradually as they become adapted to their local environments. – Mechanism-natural selection • Big changes (speciation) = steady accumulation of many small ones. |
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Punctuated Equilibrium
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Punctuated Equilibrium
• Evolution occurs in spurts. • Abrupt episodes of speciation punctuated by long periods of little change (equilibrium). |
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process: extinction
Who dies,, and why? |
process: extinction
• all members of an evolutionary group die. – ultimate cause: failure to adapt • two types: – background extinction – mass extinction |
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background extinction
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background extinction
• common, gradual extinction – most species: 1–10 my – rate: ~0.1–1.0 species per year per million species |
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mass extinctions
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• episodes of exceptionally high extinction
rates – global – many taxa – rapid |
