15 natural selectionpur

purifying selection

low fitness alleles eventually being eliminated

balancing selection

selection where 2 or more alleles are favored, preventing fixation (maintains diversity)

frequency-dependent

benefit at low frequencies AND penalty at high frequencies

heterozygote advantage

heterozygote fitness is higher than either homozygote

sexual selection

selection where fitness is increased because of conspecific choice or competition

intra-sexual selection

one sex competes with members of its own sex for mates

inter-sexual selection

one sex chooses a mating partner

how does selction influence genetic diversity?

If a trait is advantageous and helps the individual survive and reproduce, the genetic variation is more likely to be passed to the next generation

why aren’t organisms “perfectly adapted” ?

selection can only act on existing variation, adaptations are compromises, evolutionary history limits outcomes, chance is a huge factor

sexual dimorphism

phenotypic differences between the sexes associated with mate acquisition