BIOL1003 Lecture Notes - Lecture 27: Reciprocal Altruism, Kin Selection

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Altruism
Altruism
Altruism benefits another individual at a cost to oneself
Difficult to understand how it evolved because selfish behaviour is likely to lead to
higher survival and reproductive success
Therefore, you might expect that only genes for selfish behaviour should be passed
on to the next generation, not genes for altruism
No evidence that animals behave for the good of the species
E.g. lemmings throwing themselves into the sea to avoid over-exploiting the
environment- selfish individuals who did not drown themselves would be favoured
by natural selection
Kin selection
Parents are selected to care for offspring, because genes for caring are passed to
surviving offspring, and so caring evolves by natural selection
Individuals can also pass their genes on to the next generation by helping relatives
other than offspring
Kin selection favours behaviour that spreads genes through any kin, not just
offspring
The coefficient of relatedness, r, is a measure of the proportion of genes shared by
descent by two individuals
Altruistic behaviour is more likely to evolve the closer the relatedness of the donor
to recipient, and the greater the benefit to the recipient compared with cost to the
donor
Hamilton’s rule for the conditions favouring altruism: rB>C
E.g. whether a female kangaroo should warn another of the approach of a dingo
E.g. Belding’s ground squirrels give alarm calls to warn others about predators like
coyotes, but at the risk of being killed themselves
Reciprocity, “reciprocal altruism”
Reciprocity is a form of cooperation in which one individual helps another on one
occasion, and the other individual later reciprocates
Reciprocity among non-relatives could evolve if:
oThe cost of a single altruistic act is less than the benefit to the recipient,
otherwise both would lose in the long run
oThe opportunity for reciprocation is high, or an altruistic act can’t be repaid
oIndividuals are able to recognise others and refuse to help those who don’t
reciprocate
E.g. vampire bats
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Document Summary

Altruism benefits another individual at a cost to oneself. Difficult to understand how it evolved because selfish behaviour is likely to lead to higher survival and reproductive success. Therefore, you might expect that only genes for selfish behaviour should be passed on to the next generation, not genes for altruism. No evidence that animals behave for the good of the species. E. g. lemmings throwing themselves into the sea to avoid over-exploiting the environment- selfish individuals who did not drown themselves would be favoured by natural selection. Parents are selected to care for offspring, because genes for caring are passed to surviving offspring, and so caring evolves by natural selection. Individuals can also pass their genes on to the next generation by helping relatives other than offspring. Kin selection favours behaviour that spreads genes through any kin, not just offspring. The coefficient of relatedness, r, is a measure of the proportion of genes shared by descent by two individuals.

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