Sex_and_Mating_Systems[1]

Sex_and_Mating_Systems[1] - Behavioral Ecology I Sex &...

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Behavioral Ecology I Sex & Mating Systems
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Two major goals of behavioral ecology • Understanding the factors that promote sexual reproduction and the reasons for the variety of different mating systems used by animals and plants. • Understanding the factors that promote social behavior. (More on this next time.)
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Both of these areas deal with subjects that have long intrigued evolutionists, ecologists and behaviorists • Why did sex evolve in the first place and how is it maintained? • How do social systems and cooperative behavior evolve and how are they maintained?
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Why aren’t all species asexual? • It’s more efficient-only one parent is required. • It provides a greater reproductive rate for an individual’s genes. All of a parent’s genes are passed on to the next generation. In sexual reproduction only half are. • Mate finding is a bother! It takes time and energy that could be put to better uses. It often exposes individuals to greater predation. • To be favored by natural selection, sexual reproduction must increase fitness by more than double that of asexual reproduction
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Why is sexual reproduction so common? What factors favor the evolution of sexual reproduction?
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Two Hypotheses (They both could be true) Sex purges lineages of damaging genetic mutations. (Mueller’s Ratchet) Sex creates genetic variety useful in changing environments (The Red Queen Hypothesis) "It takes all the running you can do, to keep in the same place.” (Lewis Carroll ! s Through the Looking Glass)
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Mueller’s Ratchet • Every time an individual dies because of a deleterious mutation, the mutation also dies. • In sexual reproduction, recombination produces some individuals (gametes) with many mutations, others with few. • This mechanism purges a lineage of bad mutations and can give sex a big advantage. • The higher the rate of mutation the bigger the advantage
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• The environment that organisms find themselves in is constantly changing both in physical and biotic components. • A genotype that was most favored last generation
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Sex_and_Mating_Systems[1] - Behavioral Ecology I Sex &...

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