ch.23 - BIOL 1202 Chapter 23 The Evolution of Populations I...

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BIOL 1202 1-16-09/1-21-09/1-23-09 Chapter 23: The Evolution of Populations I. Smallest unit of evolution a. One common misconception about evolution is the individual organisms evolve during their lifetime b. Evolutionary processes (ex: natural selection) acts of individuals, but populations evolve Concept 23.1: Mutation & sexual recombination produce the genetic variation that makes evolution possible II. Variation within a population a. Discrete characters: classified on an either-or basis i. Ex: flower color in pea plants b. Quantitative characters: vary along a continuum within a population i. Ex: height, weight III. Mutation a. Changes in nucleotide sequence of DNA i. Source of new alleles and genes b. Point mutation: change in one nucleotide base in a gene c. Chromosomal mutations: delete, disrupt, or rearrange many loci on a chromosome d. Gene duplications: duplication of whole segments of chromosome e. Mutation rates averages 1 in every 100,000 genes per generation IV. Sexual recombination a. In sexually reproducing organisms, sexual recombination produces most of the variability in each generation b. Ex: crossing over during prophase I/ independent assortment during metaphase I What provides the selective pressure in artificial selection? HUMANS (if natural selection,
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