BIO 05 - 22 SEP - 5-Natural Selection Outcomes Lecture 5...

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04/26/10 1 5-Natural Selection Outcomes Lecture 5 September 22
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04/26/10 2 This week in BIO152 Cycle 2 labs (PRA0xxx2)- Lab 1 this week Cycle 1 (PRAxxx1) Lab 2 quiz Fri-Mon
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04/26/10 3 Outcome of selection How might selection impact a population? (Types of Selection in Freeman 25.2 pp 508 – 510) What is happening in the environment? (stable or changing) Effect on variation? (more, less, same) Effect on biodiversity? (more, less, same)
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04/26/10 4 Directional selection Shift in the average value of a trait (one extreme had poor reproductive success). e.g., during drought the mean medium finch beak shifted to be larger & deeper
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04/26/10 5 Cliff swallow example 1996 Midwest North America 6 day cold snap affected food supply (mosquitoes) Many swallows died Surviving swallows were larger on average. Hypothesis: larger swallows had greater fat supply to sustain the cold until temperature warmed & they could find food.
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04/26/10 6 Size advantage? larger size Example: frequency of similar weather patterns favouring larger birds . smaller size Example: More efficient feeders (increased maneuverability in flight) ►temporary shift in allele frequency of one (or several) alleles affecting size
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04/26/10 7
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8 Directional selection: e.g., body weight in cliff sparrows
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This note was uploaded on 04/25/2010 for the course BIO BIO152 taught by Professor Cordon during the Fall '09 term at University of Toronto- Toronto.

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BIO 05 - 22 SEP - 5-Natural Selection Outcomes Lecture 5...

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