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Evolution Notes

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Western University
Biology 3466B
Yolanda Morbey

Evolution NotesDec 2011 Types of social interactions The type depends on costs and benefits to actor and recipient and these are measured in terms of fitness The actor in any social interaction affects the recipient on the action as well as itself Cooperative is where both recipient and actor benefit Selfish is where actor benefits and recipient is harmed Altruistic is where actor is harmed and recipient benefits Spiteful is where recipient and actor are harmed The most common interaction in nature is selfish Organisms should be looking out for their own reproductive fitness selfishcooperativealtruisticspitefulAltruism results from kin selection and is kind of a selfish form Examples of altruism Cooperative breedingLarge group that raises offspring together ex seychelles warbler whitefronted beeeater Alarm callinghelps colony mates so they can hide from predator but the one doing the calling is put at risk blacktailed prairie dogs beldings ground squirrels The evolution of altruism WD Hamilton 1964 showed the conditions favouring selection for an allele that causes altruistic behaviour Coefficient of relatedness r is defined as the probability that homologous alleles in two individuals are identical by descent This differs from F the coefficient of inbreeding which is the probability that homologous alleles in the same individual are identical by descent Homologous alleles are alleles that are identical by descent Calculating r with pedigrees 1 Draw generalized pedigree of actor and recipient 2 Assign allele transfer probabilities 3 Calculate probability that homologous allele in actor and recipient is identical due to descent from a common ancestor r for halfsibling isfull siblings isand cousins is 18 Assumptionsautosomal loci in sexual organisms assume outbreeding correct parentage assignment when r is calculated for a real population Halfsiblingsif there are homologous alleles in actor and recipient the probability of this happening isxThe relatedness between mother and daughter is r
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