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Lecture

Selection on Continuous Traits and Sexual Selection.docx

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Department
Biology
Course
BIOL 103
Professor
Peter T Boag
Semester
Winter

Description
Selection on Continuous Traits and Sexual Selection - Three general modes of selection on continuous (polygenic) traits: o Stabilizing  Favours the mean or typical individual o Disruptive  Favours two or more phenotypic extremes at expense of individuals near the mean o Directional  Favours one phenotypic extreme - Stabilizing Selection: birth weights of 13,730 babies in British hospitals – ‘average is best’ - Stabilizing selection reduces the amount of variation in a trait - Disruptive Selection: seedcracker finch populations in Cameroon diverge if only large and small seeds available - Disruptive selection increases the amount of variation in a trait - Directional Selection: observations that different size Darwin’s finches eat different sized seeds on islands like Daphne Major - Directional Selection: Darwin’s finches eat different sized seeds on islands such as Daphne Major, and populations track changes in food supply o Large, hard seeds like Tribulus (= ‘puncture vine’) common in dry years o Can categorize each species of finch o It never rained, so many birds that were previously tagged died - Natural selection during a drought  average si
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