Biology 120
Handout: Behavior and Evolution: Sexual Selection
R. Irwin
Sexual Selection:
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traits evolve because they increase mating success
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mate attraction (female choice of males)
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competition for mates (male-male competition for females)
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typical result: choosy females, ornamented males
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ornaments likely to decrease survival
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why males, not females, evolve ornaments
Questions:
1. State the two main ways sexual selection occurs:
1. _________________________________
2. _________________________________
2. Traits that evolve through sexual selection:
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increase mating success and increase survival
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increase mating success but decrease survival
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decrease mating success but increase survival
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decrease mating success and decrease survival
3. Why do we see so many species in which males are brightly colored
or have structures that act as "weapons" like antlers, but so few species
in which females have these traits? (Explain what form of evolution results
in these traits and why it affects males more than females)