Forces of Evolution

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ANTH 1001
Kieran Mc Nulty

Forces of Evolution What is evolution? • a change in allele frequencies in a population over time • If the relative amounts of alleles for a gene change from one generation to the next then we can say that evolution has occurred • does not mean that their is a change in phenotype frequencies Forces of Evolution • Natural Selection ◦ causes a reduction in population variability when selection is within a population ◦ between populations, can reduce variation of both only if the pressures are the same; can increase or decrease variation between populations depending on environmental factors • Mutation ◦ Any alternation in the genetic material or processes ▪ different levels of mutation ▪ increases variation both within and between populations ◦ The modern synthesis ▪ Melding Darwinian evolutionary theory with Mendelian concepts of inheritance ▪ Mutation is the only source of novel variations ▪ Radical, large scale mutations will rarely get passed on to new generations ▪ mutation causes variation, natural selection acts on variation • Gene flow ◦ movement of genetic material from one population to another ◦ accomplished through migration (ex: seeds/birds or of a animal), cross-breeding, hybridization ◦ increases variation within population, decreases variation between population ◦ gene flow can result in new degrees of variation and even new phenotypes of traits that are polygenic (i.e. height) ◦ Ultimately, however, new phenotypic variation traces back to new genotypic variation • Genetic drift ◦ sampling error: a change in allele frequencies due to
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