Biology 1002B Lecture Notes - Lecture 14: Peppered Moth, Allele Frequency, Directional Selection
9 Apr 2016
School
Department
Course
Professor
Document Summary
Selection is the only evolutionary mechanism that can cause a population to adapt. Selection on quantitative traits: stabilizing, directional c) disruptive. Why hasn"t directional selection already removed all genetic variation for traits related to fitness: recessive alleles remain in the population, selection pressures aren"t always uniform, varies over time and across habitats (changing environments, ex. Environments are patchy, different phenotypes have better success in different situations. Recall: peppered moth, industrial evolution coloured pale tree trunks dark with soot, so pale moths were at a disadvantage while the dark moths were successful. This is a really important reason why directional selection doesn"t wipe out alleles, because there are different pressures spacially, time related changes. Adaptations (traits that increase bearer"s relative fitness) are. Predators form search images of prey: depends on the relative frequency in the population, does this individual look like every other member, there is an advantage to being rare!! (negative-frequency)
