Population Ecology I-PRS

Population Ecology I-PRS - Georgia Tech School of Biology...

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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Population Ecology
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Altruism: improving another individual’s fitness at a cost to your own fitness Altruism can only evolve when the benefits of helping another individual outweigh the costs Examples?
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Who would you choose to save from a burning building? A. Five strangers B. One sibling
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Kin selection : deriving personal fitness benefits by promoting the fitness of close relatives Coefficient of relatedness (“r”): the probability of sharing a given gene by descent
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Calculating the coefficient of relatedness 50% Mother You Sibling 50% 25%
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Calculating the coefficient of relatedness 50% Mother You Sibling 50% Father 50% 50% 50% (0.5*0.5) + (0.5*0.5) = 0.25 + 0.25 = 0.50 or 50%
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Coefficients of relatedness Relationship r Father 50% Mother 50% Offspring 50% Sibling 50% Half-sibling 25% Niece/nephew 25% Cousin 12% Self 100% Stranger 0%
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 So altruistic behavior can only evolve when (B enefits * r) - C osts > 0 OR (rewritten) C / B < r
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Kin selection limits how altruistic an individual can be Altruism can evolve here
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 So now when we talk about fitness, we have to think about inclusive fitness Inclusive fitness = (personal fitness) + (fitness of kin * r) In short : tness by helping close relatives s by being selfish with close
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Kin selection can lead to animals living in extended families In many species, relatives stay home to help defend and rear the offspring 200 bird species 120 mammal species
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Why would relatives help?
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Parents and helping relatives are in a conflict! Why might parents want to keep relatives around? Why might relatives want to leave? What do relatives have to gain by staying? Direct benefits of group living Indirect benefits of helping kin Learn how to be a better parent Inherit a rare territory Avoid the dangers of dispersing
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Helping by white-fronted bee eaters
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Parents have to convince relatives to help. .. and relatives have to agree to help What determines whether helping occurs? How much the helper can benefit the parent How much the helper can benefit by leaving The relatedness between helper and parent The dominance asymmetry between helper and parent
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Biology 1510/1511 Georgia Tech School of Biology Fall 2008 Extremely extended families = Eusocial animals Observed in many ants, bees, wasps, termites, and even one mammal!
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This note was uploaded on 09/04/2009 for the course BIO 1510 taught by Professor Unknown during the Spring '07 term at Georgia Tech.

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Population Ecology I-PRS - Georgia Tech School of Biology...

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