Lec 27 - BIS2B Fall 2009(Keen Lecture 27 Speciation II 13...

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BIS2B Fall 2009 (Keen) Lecture 27 . Speciation II 13 November More on reproductive isolation—complete pre and post-zygotic isolating mechanisms. Students should be able to: Distinguish pre-zygotic and post-zygotic isolating mechanisms Outline and illustrate 9 mechanisms of reproductive isolation Explain how more than one isolating mechanism may operate in the same taxon
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Time Cladogenesis, or speciation, is the splitting of one lineage into two species.
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Time Organisms in the two lineages accumulate differences due to selection (directional, sexual, etc.) genetic drift, or mutation. Agents of selection can be abiotic or biotic (competition, predation, parasitism, mutualism) range of phenotypes in a species a new lineage forms from a subset of the old lineage X reproductive isolation
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Distribution of populations in physical space when gene flow stops Allopatric populations Parapatric populations Sympatric populations
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Mechanisms of reproductive isolation Pre-zygotic • (6 kinds) – spatial –tempo ra l – ecological – behavioral – mechanical –game t ic Post-zygotic
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1.For species with weak dispersal abilities, a very short distance or small spatial barrier could be sufficient to render them allopatric. 1. Conversely, for organisms like birds or marine invertebrates, capable of moving long distances, allopatry may involve long distances or major barriers . • The rise of the Isthmus of Panama (3-5 MYA) shut off gene flow between the Pacific • The Isthmus separated previously connected populations of snapping shrimp, so there is no longer any gene flow. Events that divide a
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This note was uploaded on 04/21/2010 for the course BIS 2C BIS 2C taught by Professor Rizzo during the Winter '09 term at UC Davis.

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Lec 27 - BIS2B Fall 2009(Keen Lecture 27 Speciation II 13...

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