Sexual selection depends on sexual dimorphisms, which are differences in the male and female phenotypes. There is generally more variance in the reproductive success of the males rather than the females in some populations. This leads to competition among males for mates. Sexual selection involves the pressures on males and females to mate with another. Sexual characteristics do not necessarily lead to better survival of the male but will lead to greater reproductive success. This is what is seen in male peacocks that are at greater risk for predation and is called the handicap principle. The good genes hypothesis is involved in situations where certain phenotypic traits are associated with better genes and better overall fitness against things like low food supplies and predation. Both the good genes hypothesis and the handicap principle reflect honest signals to the female in order to affect her choice in mates.
HARDY-WEINBERG MODEL The Hardy-Weinberg Model describes what goes on in the genetic makeup of a population. It indicates that the allele frequencies and genotype frequencies in a population will be stable unless there are evolutionary pressures on the group. It assumes that there is no migration, no mutations, no emigration, and no natural selective pressures on a given genotype and assumes an infinite population. This basically does not work in the typical population but it can help to predict population changes in real populations. A population s genetic structure refers to the frequency of the different phenotypes rather than the frequency of the population s genes or alleles. If looking at the phenotypes, only the frequency of the homozygous recessive alleles can be determined because it is easily identifiable in the phenotype. This can be used to calculate the frequency of the remaining alleles and genotypes. There is a mathematical calculation that will determine how many of each allele there are in the population. Once the frequency of the recessive allele is known, the frequency of the dominant allele can be measured because the two frequencies add up to one. Things that will violate the Hardy-Weinberg Principle include non-random mating, the presence of mutations, gene flow in the population, natural selection, and finite population size, which leads to genetic drift. In a typical Hardy-Weinberg equilibrium, the population does not evolve. For true Hardy-Weinberg equilibrium, all of the alleles in the genome must stay at the same frequency.
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