Lecture Notes June 26

Lecture Notes June 26 - Natural selection number of...

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Natural selection- number of offspring that you leave compared to the rest of the population Fundamental Asymmetry of sex: sexual selection - disproportional investment of energetic costs between sexes for reproduction - no incentive for males to be choosy - females choice o choices on basis of phenotype of male o suggests that phenotype may be a more “fit”; male then brings allele to offspring o may be an indicator of health o nuptial gift- males bring food to female - Male competition- males compete for a female o No decision from female o Fittest male will be rewarded with right to reproduce o M. elephant seals will fight for a group of females o Most males don’t mate, only a select few actually do o Diversity comes from females o Most females do mate - Consequences of sexual selection o Most species that participate in sexual selection demonstrate sexual dimorphism -Balancing selection- alternative selection that oscillates back and forth -heterozygous advantage- increased fitness over being homozygous; prevents the loss of a certain allele -malaria preserves heterozygous advantage of sickle cell allele Negative frequency dependence- being rare is more fit - think of fish example - think of orchid example Genetic Drift - natural selection is directed by environment - genetic drift directed by randomness - shifts in allele frequency done through chance
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This note was uploaded on 09/15/2009 for the course BIOE 20c taught by Professor Marinovic during the Summer '09 term at UCSC.

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Lecture Notes June 26 - Natural selection number of...

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