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Sexual_Selection - Sexual Selection Reading Chapter 11 you...

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Sexual Selection Reading: Chapter 11, you can ignore all boxes. I will not cover section 11.5, but those of you interested in plants should read it
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Recall: The Measure of "Fitness" Fitness or Darwinian fitness is a measure of reproductive success (contribution to the next generation). This can be achieved in several ways: Survival or mortality selection Mating success or sexual selection Family size or fecundity selection
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Sexual selection Sexual dimorphism is a common occurrence in nature difference between the sexes If some characteristics of an organism do not contribute to survival or fecundity why do these traits exist? Natural selection: differential survival and reproduction Sexual selection: differential reproductive success resulting from differential abilities to find a mate Figure 10.2, pg. 375
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Sexual Selection Parental Investment : refers to the energy, time and resources devoted to mating, gestating, and caring for offspring. Parental investment is typically much greater for females. Eggs are expensive, sperm are cheap.
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Sex and Selection Sexual reproduction creates different selection pressures for males and females Females make more of a parental investment than males (e.g. orangutans) Donald Bason In 90% of mammals, males provide no parental support A females reproductive success is limited by the number of eggs A males reproductive success is potentially very large, but is limited by the number of females he can mate with: Asymmetries in male and female reproductive potential
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Asymmetry in Newts: Taricha granulosa Figure 11.5 b, c, pg. 405 Not significant Highly significant
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Asymmetry in Pipefish: Syngnathus typhie Figure 11.6 pg. 406 Highly significant
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Asymmetry in reproductive potential predicts that differences in mating behaviour will exist between the two sexes: Males: will be competitive (combat, sperm competition,
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