BIO 102 Lecture Notes - Lecture 5: Genetic Drift, Directional Selection, Speciation
26 Sep 2016
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Microevolutionary processes: mutations: create new alleles, genetic drift: when a population is small, alleles can be lost by chance. Bottlenecks: a population may rapidly and severely decrease due to disease, exploration, or sudden environment change. Genetic drift can easily occur in small populations. Human bottlenecks: some scientists hypothesize that from 75,00 year bp to 10,000 years bp humans went through a bottleneck in our evolutionary journey. Founder effect: can have a small population making it very susceptible to genetic drift is when a few individuals from a large population found a new colony. Newly founded populations don"t always represent the genetic diversity of their sources: gene flow: an allele comes in where you thought you got rid of. Enables populations to change in ways that make species better adapted to its environment. Preserves individuals with favorable phenotypes and eliminates those with unfavorable phenotypes. 3 kinds of natural selection: directional, disruptive, stabilizing.
