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Lecture 18

Biology 1001A Lecture 18

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Western University
Biology 1001A
Beth Mac Dougall- Shackleton

Biology 1001A | 2012 LECTURE NOTES Lecture 18 Cooperation & Conflict –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– - selection is fundamentally competitive, yet group living and cooperation are common Types of Social Interaction Actor Benefits Actor is Harmed Recipient Benefits cooperation altruism Recipient is Harmed selfishness spite - spite almost never happens - altruism is “a special difficulty, which at first appeared to me insuperable and actually fatal to my whole theory” - Charles Darwin Parental Care - success of offspring may come at the cost of parent survival - this parental contribution is not actually altruism due to the resulting increase in the actor’s fitness because they are helping their genes carry on via their offspring, thus this can actually be thought of as a selfish or cooperative behaviour Altruism - when an individual risks their own fitness to protect others to whom the are not related, it is altruism because the risk results in not increase in fitness to the protector - an example of this is the ground squirrel, where an adult will risk being located by a predator in order to warn the young ground squirrels of the danger Direct & Indirect Fitness - sometimes, an individual offspring will forgo their own opportunity to reproduce in order to help their parents produce more offspring - how can traits reducing fitness (offspring production) be selectively favoured? - this was traditionally explained as “sacrificing individual fitness for the good of the group”, but this is not exactly correct - instead, it is believed that there is more to fitness than simply producing direct descendants - fitness is increased by getting copies of an individual’s genes into the next generation, but there is more than one way to do this - personal reproduction results in a direct increase of fitness - additional reproduction by close relatives due to an individual’s “altruism” results in an indirect increase in fitness because the individual’s alleles, also carried by close relatives, will be copied to more offspring - inclusive fitness is the total of personal reproduction and additional reproduction by close relatives Biology 1001A | 2012 - many seemingly altruistic behaviours can be explained by kin selection, which favours traits that increase the indirect component of an individual’s fitness - in the case of the ground squirrel, it is the females that do most of the warning because they are related in some way (nieces, nephews) to the young grounds squirrels, and helping them helps the female to increase her indirect fitness Hamilton’s Rule - Hamilton’s rule determines whether “altruistic” (costly) traits are favoured by kin selection: rb > c - benefit received by donor’s relatives, (b) - weighted by degree of relationship, (r) - does this outweigh costs to donor’s direct fitness (c) ? - if rb is greater than c, then the altruistic trait should be favoured by kin selection - when rb > c the benefits to indirect fitness are high enough to outweigh the cost to personal fitness, therefore the altruistic trait should be favoured by kin selection Cooperation Between Non-Relatives - what about helping, cooperation and “altruism” between non-relatives? - sometimes altruistic behaviour is directed to non-related individuals, but why? - selection can favour “altruism” if it’s expected that the “altruism” will be reciprocated - most likely when groups are small and stable, and when individuals can recognize and remember helpers and cheaters - it has been proposed that human emotions (trust, resentment, guilt, gratitude) may have evolved as adaptations for score-keeping Back to Inclusive Fitness - much self-sacrificing (altruistic) behaviour can be explained by individuals trying to maximize their inclusive fitness - also explains conflicts between close relatives even though it would seem to contradict kin selection - parent offspring conflict of interest, such a
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