COOPERATION IN POPULATIONS Because natural selection favors certain organisms over others, one would think that this would lead only to selfish behavior in the species. This is, however, not the case, and cooperation is seen in many species. Within the organism itself, there are organelles that cooperate for the cell, genes that cooperate inside the genome, and cells in multicellular organizations that cooperate with one another. Between organisms, there are cooperative societies and cooperative breeding. Each population is filled with different actors that perform behaviors that go with or against the group. Altruism defines a behavior beneficial to a recipient but that costs the actor doing the behavior. Cheaters are those that do not cooperate or who do less than their share of the work for the population. Cooperation involves beneficial behavior that drives the evolution of the population. Some behaviors lead to direct fitness, which is the fitness an organism gains from producing offspring, while others lead to indirect fitness, which is fitness gained by aiding related individuals in the group. Kin selection involves the favoring of traits that directly benefit one s relatives. Inclusive fitness is the effect of behaviors on all members of the population. Mutualism is any type of two-way cooperation between members of the same or different species. Mutualism leads to a mutual benefit to both the actor and the recipient. The different members involved in a mutualistic relationship. There are certain genes an organism can have. The greenbeard gene is purely hypothetical gene that leads to a recognizable phenotype that is linked to a cooperative behavior in the individual. Without cooperation, natural selection would favor those who are selfish and who do not cooperate. Cheaters can have a specific trait that allows them to benefit from the other cooperators. It leads to higher fitness for the cheater, which would increase the frequency of the trait unless the frequency was so high that no one cooperated any more. Direct benefits and direct fitness favor mutually beneficial cooperation between members of the group, while indirect benefits help to explain why there is altruistic cooperation. Each act of cooperation may have differing levels of direct and indirect fitness. Indirect fitness is weighted by relatedness of the actor to the recipient. If both indirect and direct fitness is increased, the behavior is said to be mutually beneficial. In order for kin selection to work, there must be some mechanism for kin discrimination. Certain species of animals can tell who their kin is by certain vocal cues passed down from birds, for example, during the nesting period. When kin discrimination occurs, there is an increase in
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