ISCI 1A24 Lecture Notes - Lecture 3: Allele Frequency, Genotype Frequency, Genetic Drift
19 Jan 2017
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Two major points: evidence that the many species of organisms currently in existence are descendants of different and now extinct ancestral species (ex. Descent modification: natural selection: the mechanism for evolution. Individuals ina population vary: some of the variation is heritable, the variants differ in the likelihood to survive & reproduce, offspring numbers exceed the capacity of the environment/resources - majority must die. Evolution is defined as changes in allele frequencies over time. Natural selection occurs when individuals with certain alleles have increased fitness. An adaption is a genetically based trait that increases an individual"s fitness in a particular environment. Evolution by natural selection is not progressive. Individuals do not do things for the good of the species, a(cid:374)d (cid:374)ot all traits are adaptive. One could say the ultimate result of evolution is speciation. Natural selection: increases allele frequency, produces adaptation. Genetic drift: causes random fluctuations in allele frequencies (usually aused by natural disasters)
