BIOL 2050 Lecture Notes - Lecture 7: Genetic Drift, Adaptive Radiation, Overfishing
6 Aug 2015
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Atleast 2/3 ways that define evolution; genetic change over time, descent with modification: genotype --> the genetic makeup on an individual. Phenotyoe --> observable characteristics of an organism determined by their genotype. Individuals with certain heritable traits survive and reproduce more offspring than others lacking that trait. Stabilizing selection --> average phenotype is favoured: directional selection --> one extreme phenotype is favoured, disruptive selection --> both extreme phenotypes favoured (bimodal, traits that are divergent) Gene flow --> alleles move between pop"ns via movement of individuals/gametes: populations become more similar, new alleles can be introduced into a pop"n, cline --> patterns of change in a characteristic over time in a geographical region. Speciation --> the process in which one species splits into two or more species. 6 mass extinctions ***** 6 because of humans (5 natural ones) Speciation most commonly occurs when a barrier prevents gene flow between two or more pop"ns. Link 6th mass extinction to an ecological maxim.
