Lecture10_ModesOfSelection - Natural selection revisited...

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Natural selection revisited Where have we been and where are we going? First 2 weeks: 1) introduction to evolution by natural selection 2) sources of heritable variation (combinations of maternal/paternal chromosomes, crossing over, outcrossing) Today: • explore natural selection in more depth This week: • evolution as changes in allele frequencies • explore other processes, besides natural selection, that can change allele frequencies and cause evolution I. How does natural selection act on quantitative variation? A. Directional selection example: Medium ground finches on the Galápagos islands Is beak depth a variable trait? Is the variation heritable? Why is beak depth important? Studying selection in action • Drought in 1977: Tribulus cistoides fruits become • The data: This type of selection is called
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Does overall genetic variation change? Long-term changes in this finch population:
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This note was uploaded on 04/10/2008 for the course BIOL 180 taught by Professor Freeman during the Fall '07 term at University of Washington.

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Lecture10_ModesOfSelection - Natural selection revisited...

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