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7_EvolMech2

# 7_EvolMech2 - Reminders Quiz 2 available on Blackboard 11AM...

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1 Reminders Quiz 2 available on Blackboard 11AM today to 11AM tomorrow (24h) Sept 12 (Friday) is the last day to register, add classes and drop without a “W” Last year’s Midterm 1 is now posted under ‘Course Information’. Note that format will be slightly different (will include essay questions and will not involve the use of calculators)

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2 Evolutionary Mechanisms 2 23.3-23.4
3 Evolutionary Processes Mutation and sexual recombination produce new variation Selection, drift and gene flow alter allele frequencies in a population

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4 Evolutionary Processes Mutation and sexual recombination produce new variation Selection, drift and gene flow alter allele frequencies in a population
5 Natural Selection Differential survival and/or reproduction results in certain alleles being passed to the next generation in greater proportions

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6 How does selection affect HWE? Population size: 1000 individuals Alleles: A 1 A 2 Frequencies: 0.5 0.5 Genotypes: A 1 A 1 A 1 A 2 A 2 A 2 Frequencies: 0.25 0.50 0.25 Count: 250 500 250 Fitness (w) 0.6 0.8 1.0
7 What are the allele frequencies after selection? First, calculate the new genotype counts (= old genotype counts * w): A 1 A 1 A 1 A 2 A 2 A 2 Total 250(0.6) 500(0.8) 250(1.0) 150 400 250 800 Now calculate the new allele frequencies: A 1 : (2*150 + 400)/ 1600 = 700/1600 = 0.438 A 2 : (400 + 2*250)/ 1600 = 900/1600 = 0.562 The frequency of A 2 has increased!

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Strength of selection is proportional to population size QuickTimeª and a TIFF (Uncompressed) decompressor are needed to see this picture.
9 Evolutionary Processes Mutation and sexual recombination produce new variation Selection, drift and gene flow alter allele frequencies in a population

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10 Random Genetic Drift Changes in allele frequencies within populations which result from chance variation in individual survival and reproduction Most important in small populations Can result in maladaptive evolution
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