Cutter_Lecture_08 - 1 Natural Selection and Adaptation (2)...

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Unformatted text preview: 1 Natural Selection and Adaptation (2) Balance between individual and interdemic selection depends on The relative individual cost to altruism (individual sel) The relative demic benefit to altruism (interdemic sel) Individual selection usually stronger than interdemic sel Levels of selection 2 The possibility of future extinction cant affect the course of evolution in present An altruist always is at an individual disadvantage Selection can favor different traits at the level of the gene, individual, or deme Natural selection is a short sighted, mindless, goal less process Sifts through traits to favor the ones with the greatest present relative growth rate Some take home messages from LOS 3 Chemical and physical constraints can limit evolution Or create features as a byproduct of selection on another characteristic Oxygen binding of hemoglobin Red color of blood is incidental Not all traits are adaptations 4 Pre adaptation Feature that fortuitously serves a new function Selection pressures can change A characteristic that originated due to one regime of selection could be co opted for some other function Exaptation Preadaptations and Exaptations 5 Penguin wings act as swimming flippers Sharp kea beak allows it to cut skin of introduced sheep and eat their fat Independently repeated convergent evolution of a trait as a response to selection Generate hypothesis to generate predictions about observable patterns Not for prognostication of future Test with data reflecting what has occurred over the history of evolution Test statistically with independent replicates Comparative method: Identifying adaption 6 Sperm competition: a form of sexual selection Competition among sperm of multiple males to fertilize egg(s) of a single inseminated female Males of polygamous species should experience more sperm competition than monogamous species Selection favoring more sperm production Raffle model: more tickets, more chances to win...
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Cutter_Lecture_08 - 1 Natural Selection and Adaptation (2)...

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