Group selection - f(A) increases. Model this as follows:...

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Group selection = variation in the rate of increase or extinction among groups as a function of their genetic composition. Again consider how an altruistic trait could increase in frequency. Differential rates of extinction : allele A confers altruistic behavior; at a selective disadvantage to allele a within the group. Should lead to the reduction of allele A. But groups with high frequency of A may be less likely to go extinct (due to better exploitation of resources). Over all groups with high frequency of A persist and f(A) increases. Differential productivity : similar to model above but altruistic trait affects reproductive output of group. Selection against A allele within groups (selfish types have higher short term fitness) but groups with high frequency of A exploit resources more prudently and actually produce more offspring over the long term:
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Unformatted text preview: f(A) increases. Model this as follows: assume a haploid trait with A=altruist, a=selfish; p=f(A). In each population p decreases within a population through time due to selfish individuals out competing altruistic individuals. But in all populations as a whole the altruist gene increases over time. Below, the average f(A) across all populations is 0.5 at the start: Clearly, if this system were to continue for many generations, the frequency of the altruist gene would decrease within each population. But under conditions where the selection favoring selfish genes was weak and the group selection increasing the probability of staying extant (or the growth rate of the population) was strong, and altruist allele might be preserved. Because the conditions are so restrictive, group selection is presumed to be a rare phenomenon....
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