C54 Postmidterm Notes 2.docx

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University of Toronto Scarborough
Biological Sciences
Kamini Persaud

Kinship  Altruism: self-sacrificing behavior where an individual permanently loses opportunities to produce offspring of its own because it helped another.  Altruism is a Darwinian puzzle: How is this behavior not lost over time if it is detrimental to one’s reproductive success? Possible explanation: By helping your relatives, you are increasing your own fitness if their young survive. Coefficient of relatedness: the probability that an allele in one individual is present in another because they both inherited it from a common ancestor.  Kin Selection: Altruism supplied to relatives other than offspring.  Direct fitness: Fitness gained through personal reproduction  Indirect fitness: Fitness gained by helping non descendent kin survive (ie. Kin selection)  Inclusive fitness: An individual’s total contribution of genes to the next generation as a result of both of the above.  Hamilton’s Rule: A rare allele for altruism will become more common only if the indirect fitness gained by the altruist is greater than the direct fitness it loses as a result of its self sacrificing behavior.   Inclusive Fitness and the Pied Kingfisher: Some males can’t secure mates and become primary helpers by protecting their MOM’s nests. They could also act as secondary helpers (protecting other, non related, couples) or delayers (wait till next year). Primary helpers work harder than the other two groups. Primary benefit more because the indirect gain is greater than the direct loss.  Examples: Jays. In one species that lacks helpers, breeding individuals have high prolactin levels while non breeders have low levels. It has been shown that in non breeders in a related species which DOES have helpers, prolactin levels rise even though they are not breeding. This is priming the non breeding individual to act as a helper. Helpers get some o direct gain because they sometimes get to use the same nest that their parents built. There is also o indirect gain:  siblings survive. Another indirect gain:  parents may survive longer due to the additional care given by the helper to the nest (so even more siblings can be made).  In the above species, an experiment was done where helpers were experimentally removed from nests. The reproductive success of the couple reduced by 50% when helpers were removed, so helpers are vital.  Facultative altruists: helpers who CAN become breeders but choose to remain as helpers because they are not able to secure a high quality nest themselves to breed. Test experimentally: if young birds remain on their natal territories because they cannot find suitable nesting habitats, then yearlings given an opportunity to claim good open territories should promptly become breeders. Hypothesis was supported in an experiment with warblers.  The Evolutionary History of Helping at the Nest: Helping systems are relatively rare. One scientist: evolution of helping tied to environmental factors. If environment is unstable, then helping occurs because it may be too dangerous to start your own nest.  Transactional Theory of Social Behaviour: Members
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