Solomon IM Ch 19

# Solomon IM Ch 19 - ,Berg,andMartinsBiology,9thEdition 19...

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Instructor’s Manual for Solomon, Berg, and Martin’s Biology, 9 th Edition 200 19 Evolutionary Change in Populations Lecture Outline I. Genotype, phenotype, and allele frequencies can be calculated. A. A population’s gene pool consists of all the alleles present in the population. 1. Population is the same species living in the same geographic area at the same time. 2. Genotype frequency is the proportion of a particular genotype in the population. 3. Phenotype frequency is the proportion of a particular phenotype in the population. 4. Allele frequency is the proportion of a specific allele in a population. II. The Hardy Weinberg principle describes genetic equilibrium. A. Godfrey Hardy, an English mathematician, and Wilhelm Weinberg, a German physician, derived this model independently in 1908. B. The Hardy Weinberg principle describes the situation of no evolution (e.g., genetic equilibrium). C. p is the frequency of the dominant allele, and q is the frequency of the recessive allele; frequencies range from 0 to 1. D. p + q = 1; therefore ( p + q ) 2 = 1 E. p 2 + 2 pq + q 2 = 1; p 2 is the frequency of the dominant homozygote, 2 pq is the frequency of the heterozygote, and q 2 is the frequency of the recessive homozygote. F. Any sexually reproducing population in which the allele frequencies conform to this equation is at genetic equilibrium. G. The assumptions of this model 1. Random mating of all genotypes 2. No net mutations 3. Large population size due to statistical constraints 4. No migration—no exchange of alleles with other populations 5. No natural selection H. Human MN blood groups are an illustration of the Hardy Weinberg principle. 1. This appears to be at equilibrium in the human population. 2. Lack of medical significance of this trait leads to no adaptive advantage to possessors of either gene. 3. There is no significant difference between phenotypes, hence no natural selection. III. Microevolution occurs when a population’s allele or genotype frequencies change. A. Evolution occurs when a population does not meet all of the assumptions of the Hardy Weinberg principle. B. These small changes are referred to as microevolution.

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Chapter 19: Evolutionary Change in Populations 201 IV. Nonrandom mating changes genotype frequencies. A. When individuals reproduce with individuals of similar genotypes by choice or location, deviations from equilibrium occur. 1. This may lead to inbreeding, which may lead to increased homozygosity. 2. This may lead to inbreeding depression and lowered fitness in the population, common in some plants. B. Assortative mating occurs when mating is influenced by similar phenotypes. 1. Positive assortative mating also increases homozygosity. 2.
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Solomon IM Ch 19 - ,Berg,andMartinsBiology,9thEdition 19...

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