BIO 121 Lecture Notes - Lecture 16: Disruptive Selection, Stabilizing Selection, Directional Selection

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Populations evolve by migration, nonrandom mating, genetic drift, mutations,a dna natural selection. Natural selection works on variation already present in a population. (only a population can evolve, not individuals) This is because evolution= genetic change over time. Microevolution= altered frequency of alleles in a population over generations. Mutations, gene rearrangements change the sequence of dna ( must occur in gametes, so as to be passed on to the next generation) Rapid reproduction leaves room for dna replication errors. Mutations that alter the phenotype are often harmful. Harmful mutations can be hidden from selection in recessive allele. Mutations that result in a change in phenotype are sometimes beneficial. Genetic variation is required for a population to evolve, but does not guarantee that it will. Only populations can evolve- although evolution acts on individuals (no change in population if it occurs to one individual), the individuals cannot change the frequency of their alleles.

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