Gene Flow
It is often argued whether ants and other social insects are altruistic in their contribution to the colony rather than trying to reproduce and directly pass on their own genes to their offspring. Yes, they seem to be altruistic, in they are helping their sisters at their own expense without directly passing on their genes. No, they aren't altruistic, in that they are passing on their own genes by allowing the colony to survive and expand to new colonies. This type of natural selection is called Kin Selection. Genes are selected in nature according to their ability to contribute to the success of the species. If an altruistic gene helps a colony to survive, then that gene will be passed onto kin which will in turn have the altruistic gene that will help that colony survive. If the gene for altruism works against the success of the colony then the individuals with the gene will not be successful and the gene will be selected against.
One possible explanation for kin selection arises from the fact that all workers are females. It turns out that the workers are more closely related to each other than they would be to their own offspring. This means that they are more successful in making more genetically similar individuals by helping the colony than by having their own offspring.
Specifically, males arise from unfertilized eggs so they have only a half complement of genes, all from their mother. Female workers arise from fertilized eggs and therefore have a full complement of genes of which half come from their mother and half come from their father. Workers always get the exact same half of their gene complement from their father since he only has a half to begin with. Workers are, therefore, at least fifty percent related to each other since half of their genes always come from their father. Workers can end up with either half of their mother's genes which means that they will be on average 75 percent related to each other. If the workers did have the opportunity to reproduce, (which they don't), the best they can do is to contribute 50 percent of their genes to their offspring.
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Science Education Connection Department of Biochemistry The University of Arizona Tuesday, April 29, 1997 warder@u.arizona.edu
http://biology.arizona.edu/sciconn/lessons/shindelman/ |