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Chapter 23 The Evolution of Populations

Explore the unit of evolution, the individual or the population, in population genetics. Learn about the Hardy-Weinberg theorem, genetic drift, founder's effect, gene flow, and more.

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Chapter 23 The Evolution of Populations

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  1. Chapter 23The Evolution of Populations

  2. Question? • Is the unit of evolution the individual or the population?

  3. So what do we study?

  4. Population Genetics

  5. Modern Synthesis

  6. Population

  7. Species

  8. Gene Pool

  9. Microevolution

  10. Hardy-Weinberg Theorem

  11. Basic Equation

  12. Expanded Equation

  13. Genotypes

  14. Example Calculation • Let’s look at a population where: • A = red flowers • a = white flowers

  15. Starting Population • N = 500 • Red = 480 (320 AA+ 160 Aa) • White = 20 • Total Genes = 2 x 500 = 1000

  16. Dominant Allele • A = (320 x 2) + (160 x 1) = 800 = 800/1000 A = 80%

  17. Recessive Allele • a = (160 x 1) + (20 x 2) = 200/1000 = .20 a = 20%

  18. A and a in HW equation • Cross: Aa X Aa • Result = AA + 2Aa + aa • Remember: A = p, a = q

  19. Substitute the values for A and a • p2 + 2pq + q2 = 1 (.8)2 + 2(.8)(.2) + (.2)2 = 1 .64 + .32 + .04 = 1

  20. Dominant Allele • A = p2 + pq = .64 + .16 = .80 = 80%

  21. Recessive Allele • a = pq + q2 = .16 + .04 = .20 = 20%

  22. Result

  23. Importance of Hardy-Weinberg

  24. Example

  25. PKU Frequency

  26. Dominant Allele

  27. Expanded Equation

  28. Final Results

  29. Practice Problem • A fruit fly population has a gene with two alleles A1 & A2. 70% of the gametes produced in the population carry A1. What is the proportion of the population that are heterozygous?

  30. Practice Problem • In a H-W population with two alleles, A & a, that are in equilibrium, the frequency of allele a is 0.7. What is the percentage of the population that is heterozygous for this allele?

  31. AP Problems Using Hardy-Weinberg • Solve for q2 (% of total). • Solve for q (equation). • Solve for p (1- q). • H-W is always on the national AP Bio exam (but no calculators are allowed).

  32. Hardy-Weinberg Assumptions

  33. If H-W assumptions hold true:

  34. Microevolution

  35. Causes of Microevolution

  36. Genetic Drift

  37. By Chance

  38. Bottleneck Effect

  39. Result

  40. Importance

  41. Founder's Effect

  42. Result

  43. Importance

  44. Gene Flow

  45. Result

  46. Mutations

  47. Result

  48. Nonrandom Mating

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