Chapter 15 - Chapter 15 How Organisms Evolve 15.1 How are...

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Chapter 15 How Organisms Evolve 15.1 How are populations, genes, and evolution related? 15.2 What causes evolution? 15.3 How does natural selection work?
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15.1 How Are Populations, Genes, and Evolution Related? Genes and the environment interact to determine traits The gene pool is the sum of the genes in a population
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The Gene Pool For example, coat color in hamsters: A population of 25 hamsters contains 50 alleles of the coat color gene (hamsters are diploid) If 20 of those 50 alleles code for black coats, then the frequency of the black allele is 0.40 or 40% [20/50 = 0.40]
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15.1 How Are Populations, Genes, and Evolution Related? Evolution is the change over time of allele frequencies within a population The equilibrium population is a hypothetical population that does not evolve
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The Hardy-Weinberg Principle A mathematical model (1908) proposed independently by Godfrey H. Hardy (English mathematician) Wilhelm Weinberg (German physician)
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Hardy-Weinberg Principle (no evolving) 1. There must be no mutation 2. There must be no gene flow 3. The population must be large 4. All mating must be random 5. There must be no natural selection
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Section 15.2 Outline 15.2 What Causes Evolution? Mutations Are the Source of Genetic Variability Gene Flow Between Populations Changes Allele Frequencies Allele Frequencies May Drift in Small Populations Mating Within a Population Is Almost Never Random All Genotypes Are Not Equally Beneficial
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Causes of Evolution Five factors contribute to evolutionary change: 1. Mutation 2. Gene flow 3. Small population size 4. Nonrandom mating 5. Natural selection
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Source of Genetic Variability Mutations are rare changes in the base sequence of DNA in a gene Usually have little or no immediate effect Are the source of new alleles Can be passed to offspring only if they occur in cells that give rise to gametes Can be beneficial, harmful, or neutral Arise spontaneously, not as a result of, or in anticipation of, environmental necessity
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15.2 What Causes Evolution?
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This note was uploaded on 01/11/2012 for the course BIO 160 taught by Professor Howardhaemmerle during the Fall '12 term at Bellevue College.

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Chapter 15 - Chapter 15 How Organisms Evolve 15.1 How are...

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