Chapter 23 notes

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Unformatted text preview: Click to edit Master subtitle style 6/13/11 Chapter 23 The Evolutions of Populations 6/13/11 The Smallest Unit of Evolution • One common misconception about evolution is that individual organisms evolve during their lifetime. • Evolutionary processes (e.g., natural selection) act on individuals, but populations evolve. 6/13/11 Populations • A group of individuals of the same species living in a certain defined area 6/13/11 Concept 23.1 • Mutation and sexual recombination produce the genetic variation that makes evolution possible 6/13/11 Mutation • Mutations: changes in nucleotide sequence of DNA – Source of new alleles and genes • Point mutation: change in one nucleotide base in a gene (also called a nucleotide substitution) • Chromosomal mutations: delete, disrupt, or rearrange many loci on a 6/13/11 Sexual Recombination • In sexually reproducing organisms, sexual recombination produces most of the variability in each generation – Crossing over during prophase I – Independent assortment during metaphase I 6/13/11 Variation within a Population • Discrete characters: classified on an either-or basis (determined by a single gene). – E.g., flower color in pea plants • Quantitative characters: vary along a continuum within a population (show a much wider range of phenotype because it is determined by many genes rather than a single gene)— 6/13/11 Concept 23.2 • The Hardy-Weinberg equation can be used to test whether a population is evolving – If there are no differences, we can conclude that the real population is not evolving. – If there are differences in what the genetic makeup of a population would be if it were not evolving at a particular 6/13/11 Hardy-Weinberg Equilibrium • H-W equilibrium: describes a population that is not evolving (i.e., population that is not evolving (i....
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This note was uploaded on 06/13/2011 for the course BIOL 1202 taught by Professor Gregg during the Spring '08 term at LSU.

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