13_Natural_Selection_II

13_Natural_Selection_II - Nat NaturalSelectionRevisited...

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at ral Selection Re isited Natural Selection Revisited d ’ ti Today’s questions: I. How does natural selection act on quantitative variation? Ct i t lt i b tl lt i II. Constraints on evolution by natural selection III. Common misunderstandings
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I. How does selection act on quantitative traits? Directional selection A. Directional selection 1. What is “ irectional” about directional about directional selection?
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2. What happens to overall variation? 3. Do allele frequencies change? Explain. 4. If drought conditions continued, would overall variation eventually NOT be normally distributed?
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Long term changes in this population: 4. What happened here? 5. And here? 6. And here?
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B. Stabilizing selection Study organism: Mayflies males form mating swarms. Females fly into the swarms, copulate in the air, and then lay their eggs in water nearby. he study: document size of males in swarms and of The study: document size of males in swarms and of males that copulate successfully.
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The data: black bars = all males open bars = copulating males
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II. Constraints on evolution by natural selection
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This note was uploaded on 05/25/2010 for the course BIO 180 taught by Professor Bradshaw during the Spring '09 term at University of Washington.

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13_Natural_Selection_II - Nat NaturalSelectionRevisited...

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