1323441104_CHAPTER_12_SPR

1323441104_CHAPTER_12_SPR - EVOLUTION/LECTURE1 Evolution...

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EVOLUTION/LECTURE1 file:///E|/CH12-BEHAVIOR-SPRING-2008/CHAPTER%2012%20SPR_2008.HTML[12/8/2011 2:55:14 PM] Evolution ( PCB 4674 ). Chapter 12. Kin selection and social behavior Main topics of lecture: I: Kin selection and the evolution of altruism: 1.- Inclusive fitness 2.- Examples of inclusive fitness: Alarm calling in belding's ground squirrels and helping behavior in white-fronted bee eaters II: Evolution of eusociality: 3.- Introduction to eusociality 4.- Haplodiploidy and eusocial Hymenoptera III: Reciprocal altruism 5.- Introduction to reciprocal altruism 6.- Blood-sharing in vampire bats I: Kin selection and the evolution of altruism: 1.- Inclusive fitness 1.1.- Social interactions create the possibility for conflict and cooperation among individuals of a given species. In fitness terms, and interaction between individuals has four possible outcomes: i.- Cooperation or mutualism : Actions that result in fitness gains for both participants. ii.- Altruism . The individual instigating the action ( actor ) pays a fitness cost and the individual on the receiving end ( recipient ) benefits. Examples would be some birds that help at their parents nests (known as helpers ) to humans who dives into a river to saves a drowning child. iii.- Selfishness . Is the opposite to altruism: The actor gains and the recipient loses. iv.- Spite . Is the term for behavior that results in fitness losses for both participants. 1.2.- It is straight forward to understand why spite has not evolved: An allele that results in fitness losses for both actor and recipient would quickly be eliminated by natural selection. But altruism would seem equally difficult to explain , because one
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EVOLUTION/LECTURE1 file:///E|/CH12-BEHAVIOR-SPRING-2008/CHAPTER%2012%20SPR_2008.HTML[12/8/2011 2:55:14 PM] of the participants suffers a fitness loss. Altruistic behavior appears to be common, so the first question we need to address is: Why does altruism exist in nature? 1.3.- Altruism is a CENTRAL PARADOX of Darwinism. It would seem impossible for natural selection to favor an allele that results in behavior benefiting other individuals at the expense of the individual carrying the allele. For Darwin altruism presented a " special difficulty, which at first appeared to me insuperable, and actually fatal to my whole theory " Fortunately Darwin was able to hint a resolution to this paradox: Selection could favor traits that result in decreased personal fitness if they increase the survival and reproductive success of close relatives 1.4.- The key parameter to understand the hypothesis of selection favoring the fitness of close relatives is known as the coefficient of relationship (r) . This coefficient will give us the probability that the homologous alleles in two individuals are identical by descent. 1.5.- Calculating r requires a pedigree that includes the
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1323441104_CHAPTER_12_SPR - EVOLUTION/LECTURE1 Evolution...

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