chapter 17 edited

chapter 17 edited - Processes of Evolution Chapter 17 17.1...

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Unformatted text preview: Processes of Evolution Chapter 17 17.1 Populations Evolve Population Individuals of the same species in the same area Generally the same number and kinds of genes for the same traits Gene pool All the genes of a population Variation in Alleles Individuals who inherit different combinations of alleles vary in details of one or more traits Polymorphism: Several alleles in a population Mutations are the original source of new alleles Lethal mutations result in death Neutral mutations neither help nor hurt Phenotypic Variation in Populations Microevolution Changes in allele frequencies of a population Mutation Natural selection Genetic drift Gene flow 17.2 When Is A Population Not Evolving? Genetic equilibrium A state in which a population is not evolving Never occurs in nature Deviations from theoretical genetic equilibrium are used to study how a population is evolving Hardy-Weinberg Equilibrium Equation If frequency of alleles in a population changes, the population is evolving p + q = 1.0 p 2 + 2 pq + q 2 = 1.0 p and q = frequencies of alleles A and a 2 pq = carrier frequency Is This Population Evolving? 17.3 Natural Selection Natural selection Differential survival and reproduction among individuals of a population that show variations in details of their shared traits ( alleles ) Allele frequencies Maintained by stabilizing selection Shifted by directional or disruptive selection Modes of Natural Selection 17.4 Directional Selection Shifts range of variation in traits in one direction Individuals at one end of the range are favored; those at the other end are not Examples: Peppered moth, pocket mice (predation) Antibiotic resistance Directional Selection Peppered Moth Pocket Mice 17.5 Selection For or Against Extreme Phenotypes Stabilizing Selection Works against both extremes in the range of phenotypic variation Favors intermediate forms Disruptive selection Favors forms at extremes of the range Stabilizing and Disruptive Selection...
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This note was uploaded on 03/10/2011 for the course BIOL 1409 taught by Professor Staff during the Spring '11 term at Dallas Colleges.

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chapter 17 edited - Processes of Evolution Chapter 17 17.1...

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