3-Evolution Pt. 2 (Chapter 22-25)

3-Evolution Pt. 2 (Chapter 22-25) - Evolution II Chapters...

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Bioenergetics 1 BIOL 112 Evolution II Chapters 22–25 BIOL 112 Darwinian Theory ± By the end of the 19 th Cent., Darwin’s Theory was in trouble ± Couldn’t adequately explain inheritance ± If favorable gene combinations are selected for, how keep them together through several generations? ± Standard 19 th Cent. Inheritance model was Blending Inheritance ± No one read or understood Mendel’s work ± By turn of 20 th Cent., “rediscovery” of Mendel: Hugo de Vries, Dutch geneticist discovered mutations (new alleles), and found and publicized Mendel’s papers BIOL 112 Darwin vs. Mendel? ± Evolutionists realized need to revise Darwin’s Theory to incorporate genetics information ± Synthesis of Darwin and Mendel done in 1920s and 1930s by Fisher, Wright and Haldane ± Product is Neo-Darwinian Theory of Evolution: ± Darwin Natural Selection acting on variations in phenotypes ± Mendel Genetic Variability: mutations and recombinations; and Principles of Heredity ± Evolution: a change in the genetic content of a population over time BIOL 112 Mendel Applied to Populations? ± Godfrey Hardy, British Mathematician ± Wilhelm Weinberg, German Physician ± In 1908, both independently developed mathematical application of Mendel’s principles to populations ± Hardy-Weinberg model of Population Genetics BIOL 112 Terms ± Gene Pool Sum of all genetic information in a reproducing population ± Allele (Gene) Frequencies Relative proportion of alleles in a population ± Genotype Frequencies Relative proportion of genotypes in a population ± What happens if allele frequencies change? Evolution , by definition ± Population Genetics Application of Mendelian principles to populations of organisms BIOL 112
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Bioenergetics 2 BIOL 112 BIOL 112 Differences from Classical Mendelian Genetics ± We are considering all eggs and all sperm (pollen) in the reproductive population, not just those from two individuals ± Conditions to be met to work mathematics: ± Breeding population is very large ± No mutations in population ± No immigration or emigration ± Reproduction success (contribution of eggs or sperm to pool) not related to genotypes/phenotypes of members of population * Notice that Campbell text lists 5 conditions: text splits last condition into two separate criteria BIOL 112 Hardy-Weinberg Equilibrium ± If all conditions are met, population will reach stable state in which allele frequencies and genotype frequencies will not change from generation to generation: H-W Equilibrium ± Population in equilibrium will not evolve unless outside forces intervene. Thus, “outside forces” will tend to cause evolution (allele frequency change) BIOL 112 Mathematical Derivation of Hardy-Weinberg Model ± Binomial Equation ± Starting with allele frequencies: f(A) = p; f(a) = q; ± (p + q) 2 = 1; ± p 2 + 2pq + q 2 = 1 ± Thus, one can identify genotype frequencies: ± f(AA) = p 2 ; ± f(Aa) = 2pq; ± f(aa) = q 2 BIOL 112 Back Calculation from HW ± Allele Frequencies:
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3-Evolution Pt. 2 (Chapter 22-25) - Evolution II Chapters...

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