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G - Examples of selection at different hierarchical levels...

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G. C. Williams responded to this idea with Adaptation and Natural Selection (1966) arguing that this behavior would be less fit than a cheating behavior where individuals did not reduce their reproductive output at times of high density/low food availability. In general selection at the level of the individual would be much stronger than selection at the level of groups. In keeping with Williams' claim that one should always seek the simplest explanation for selective/adaptive explanations, individual selection is usually sufficient to account for patterns. Group selectionist thinking leads to statements such as "good for the species" when it is entirely likely that it may be good for the individual as well: reduced reproductive effort in times of low food may increase an individual's reproductive output at a later date.
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Unformatted text preview: Examples of selection at different hierarchical levels: Genic selection is selection at the gene level; best example is meiotic drive (segregation distortion) where one gametic type (often one chromosomal type) is transmitted into the gamete pool (or next generation) in excess (or deficiency). The T locus in mice: affects tail length but also viability. TT homozygotes have normal long tails; Tt heterozygotes have short tails and transmit ~ 90% of the t allele to their sperm; tt homozygotes are sterile. Meiotic drive will increase frequency of t allele to point where that become frequent enough to occur as tt homozygotes with appreciable frequency, whereupon selection works against t alleles. Opposite Selection at two levels selection for at the level of the gene; against at the level of the genotype (organism)....
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