Lec 26 - BIS2B Fall 2009(Keen Lecture 26 Speciation 9...

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BIS2B Fall 2009 (Keen) Lecture 26 . Speciation 9 November Concept of a lineage, anagenesis, extinction, stasis, cladogenesis and reproductive isolation. Students should be able to: Describe the four fates of a lineage over evolutionary time predict the effects of gene flow on population differentiation explain the process of cladogenesis outline and illustrate 9 mechanisms of reproductive isolation
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What is a lineage? A group of organisms connected by descent from a common ancestor. This slightly vague definition is useful at a range of levels your family is a lineage, your ethnic group is a lineage, the human species is a lineage; all primates form a lineage, all mammals form a lineage, all chordates form a lineage.
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Then Now TIME A genetic lineage
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Four possible fates of a lineage Total phenotype Time Now stasis anagenesis extinction cladogenesis Then What kind of selection would produce anagenesis?
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What kind of long-term selection would result in stasis? • a. Directional selection • b. Divergent selection • c. Stabilizing selection • d. Sexual selection • e. Frequency-dependent selection
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There are many definitions of a species The biological definition of a species is a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups. This means that fertile hybrids between two species do not form or persist. A population is a unit of a species comprising organisms that interbreed.
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a large area with populations that could interbreed (a species would include the entire range occupied by the organisms) ?
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