Bio171-F08-lec22 - Lecture 22: Friday, October 24, 2008...

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Unformatted text preview: Lecture 22: Friday, October 24, 2008 Biology 171 Today’s Topic: Evolutionary Processes I Announcements This Week in Discussion: Population Genetics Simulations Exam II MC results: Mean = 40/60 = 80% Results of both parts will be posted Monday Text Reading Lec 22 : 2 nd ed: Chapter 24 (520-527) 3 rd ed: Chapter 25 (508-511; 520-523) Lec 23: 2 nd ed: Chapter 15 (328-335); Ch. 16 (355-357) Ch. 24 (531-3) 3 rd ed: Chapter 15 (319-326); Ch. 16 (347-349) Ch. 25 (515-518) Modern Synthesis Different Types of Selection Heterozygote Advantage Directional/Disruptive/Stabilizing Sexual Selection (Inter/Intra) Reductive Evolution + The modern evolutionary synthesis represents the combination of Charles Darwin's theory of the evolution of species by natural selection, Gregor Mendel's theory of genetics as the basis for biological inheritance, and mathematical population genetics. Darwin, Mendel & Population Genetics The Modern Synthesis According to the modern synthesis, genetic variation in populations arises spontaneously through random mutation and is constantly reshuffled into new allelic combinations by meiosis. Evolution consists primarily of changes in the frequencies of alleles between one generation and another as a result of genetic drift, gene flow and natural selection . Speciation is usually due to the gradual accumulation of small genetic changes and most easily occurs when populations are reproductively isolated, e.g. by geographic barriers. The modern evolutionary synthesis represents the combination of Charles Darwin's theory of the evolution of species by natural selection, Gregor Mendel's theory of genetics as the basis for biological inheritance, and mathematical population genetics. Darwin, Mendel & Population Genetics The Modern Synthesis Natural selection occurs when individuals with certain heritable phenotypes survive and reproduce better than others. The alleles responsible for the increased reproduction then increase in frequency. Different patterns of natural selection exist, each with its own causes and population genetic consequences. Natural selection, in some cases, can act to maintain genetic variation in a population. Heterozygote advantage is a pattern of natural selection in which heterozygous individuals have higher Ftness than homozygous individuals. We already covered a prominent case of heterozygote advantage (Sickle-Cell anemia in malarial habitats) Balancing Selection , so called because the higher heterozygote Ftness is ‘balanced” by the lowered Ftness of the homozygous conditions. Directional selection occurs when natural selection increases the frequency of one allele....
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This note was uploaded on 01/30/2012 for the course BIO 171 taught by Professor Josephinekurdziel during the Fall '08 term at University of Michigan.

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Bio171-F08-lec22 - Lecture 22: Friday, October 24, 2008...

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