1. Evolution of Populations Chapter 23

2. Macroevolution Evolution on a large scale Changes in plants & animals Where new forms replace old Major episodes of extinction

3. Microevolution Changes within a population Changes in allele frequencies Leads to adaptation of an organism

4. Variation Gene variation Driving force behind evolution New genes & alleles can arise by mutation or gene duplication Sexual reproduction

6. Genetic Variation from Sexual Recombination

7. Population genetics Study of the properties of genes in populations

8. Population Group of individuals Same species Interbreed Fertile offspring

9. Population Contains a great deal of variation Variation-raw material for evolution

10. Gene pool All the alleles Of all individuals within a population

11. Hardy-Weinberg Principle Determines if population is evolving Frequencies of alleles in population Used for baseline of genes in a population

12. Hardy-Weinberg Equilibrium When proportions of genotypes remain the same Generation to generation

13. Hardy-Weinberg Original proportions of genotypes in a population remain constant if 1. Large population 2. Random mating 3. No mutations 4. No gene flow 5. No natural selection

14. Hardy-Weinberg P+q=1alleles p=dominant q=recessive p 2 + 2pq + q 2 = 1genotypes

15. Hardy-Weinberg 84 black16 white (100 total)

16. Hardy-Weinberg p 2 + 2pq + q 2 = 1 P + q=1 q 2 =.16 q =.4 p =.6 p 2 =.36 2pq =.48

17. Hardy-Weinberg If the dominant allele is 30% of the gene pool What is % dominant phenotype % recessive phenotype % hybrid

18. Hardy-Weinberg Factors that affect evolutionary change 1. Mutations 2. Nonrandom mating 3. Gene flow 4. Genetic drift 5. Natural selection

19. Mutation Occurs at a low rate Not a strong influence on evolutionary change

20. Nonrandom mating Individuals with one genotype mate with another at a greater rate Not a strong influence on allele frequency

21. Gene flow Movement of alleles from one population to another Populations exchange genetic information Example New animal comes into population Mates & survives

22. Gene flow Bees and pollen Seeds Reduces genetic differences between populations

23. Gene flow Insecticide resistant alleles Mosquito West Nile & Malaria Spreading the allele

24. Gene flow Advantage when a beneficial mutation enters a population Select for the allele Disadvantage when an inferior allele enters the population Select against the allele

25. Genetic drift Change in allele frequency due to chance alone Small populations

26. Genetic drift Only a few possible alleles are present Example: Red, blue, yellow seeds If blue & yellow are isolated from red Eventually the population will only have blue or yellow and no red

27. Genetic drift May see a rise in harmful alleles Lose alleles

28. Fig. 23-8-3 Generation 1 C W C R C R C W C R C R C W p (frequency of C R ) = 0.7 q (frequency of C W ) = 0.3 Generation 2 C R C W C W C R p = 0.5 q = 0.5 Generation 3 p = 1.0 q = 0.0 C R

29. Genetic drift 1. Founders effects Few individuals leave a population New isolated population Few alleles present Island populations Amish (polydactyly)

30. ..\..\..\Desktop\polydactyl.jpg

31. Genetic drift 2. Bottleneck Occurs when a few surviving individuals have only a few genes Loss of genetic variability Occurs when a natural event happens –Flood, drought, disease etc.

32. Fig. 23-9 Original population Bottlenecking event Surviving population

33. Genetic drift Northern elephant seal California Reduced to few seals in a population due to hunting Has rebounded in numbers Organisms with limited genetic variation

35. Fig. 23-10a Range of greater prairie chicken Pre-bottleneck (Illinois, 1820) Post-bottleneck (Illinois, 1993) (a)

37. Selection Natural selection the process that causes evolutionary change Adaptive evolution

38. Selection Natural selection to happen & cause evolutionary change 1. Must have variation in individuals among population Enables choice of traits that are better able to survive

39. Selection 2. Variation causes different number of offspring surviving 3. Variation must be genetically inherited

40. Selection Individuals with a certain phenotype Leave more surviving offspring than other phenotypes

41. Relative fitness Reproductive success Number of surviving offspring left for the next generation Green vs brown frogs Green leave 4 offspring Brown leave 2.5 offspring More green mating eventually lose the brown phenotype

42. Relative fitness 1. Survival (how long) 2. Mating success 3. Number of offspring Examples: larger organisms mate more Larger fish or frogs leave more offspring

43. Forms of selection 1. Disruptive selection 2. Directional selection 3. Stabilizing selection

44. Forms of selection 1. Disruptive selection Eliminates intermediate type Favors extremes Example: African-bellied seed cracker finch Large beak Large seeds Small beak Small seeds

45. Original population (b) Disruptive selection Phenotypes (fur color) Frequency of individuals Evolved population

46. Forms of selection 2. Directional selection Favors one extreme

47. Original population (a) Directional selection Phenotypes (fur color) Frequency of individuals Original population Evolved population

48. Forms of selection 3. Stabilizing selection Eliminates both extremes Example: birth weight of newborns Small & large newborns can be harmful Increased death rate Intermediate BW best survival

49. Original population (c) Stabilizing selection Phenotypes (fur color) Frequency of individuals Evolved population

50. Selection Environment imposes conditions Determines selection Cause evolutionary change.

51. Selection 1. Selection to avoid predators Adaptation that decreases the chance of being captured

52. Selection 2. Selection to match climatic condition Enzyme alleles Vary depending on geographic location Fish enzyme for LDH Coverts pyruvate to lactate Works better in colder weather Fish swim faster

53. Selection 3. Selection for pesticide resistance Housefly developed a resistant target receptor Do not absorb the insecticide Rats have developed resistance to Warfarin (blood thinner)

54. Sexual selection Sexual dimorphism: Differences in secondary sexual characteristics Intrasexual selection: Selection between same sex Competing for mates Male fighting

55. Sexual selection Intersexual selection: Selection of mate Females choosing male mate “good genes”

56. Fig. 23-15

57. Fig. 23-19

58. Maintaining variation 1. Frequency-dependent selection 2. Oscillating selection 3. Heterozgote advantage

59. Frequency-dependent selection Fitness of a phenotype depends on frequency within population Negative frequency-dependent selection Rare phenotypes favored Predator preys on the more common phenotype Allowing less common phenotype to thrive

60. Frequency-dependent selection Positive frequency-dependent selection Predator feeds on rare phenotype Favoring common phenotype

61. Oscillating selection When one phenotype is favored at one time Another phenotype is favored at a different time Birds beak size and drought

62. Heterozygote advantage Favored genotype has both alleles Example: sickle cell anemia Heterozygous for disease does better against malaria

63. The Sickle-Cell Allele Events at the Molecular Level Sickle-cell allele on chromosome Template strand Effects on Individual Organisms Consequences for Cells Fiber An adenine replaces a thymine. Wild-type allele Sickle-cell hemoglobin Low-oxygen conditions Sickled red blood cell Normal red blood cell Normal hemoglobin (does not aggregate into fibers)

64. The Sickle-Cell Allele Evolution in Populations Key Frequencies of the sickle-cell allele Distribution of malaria caused by Plasmodium falciparum (a parasitic unicellular eukaryote) 3.0–6.0% 6.0–9.0% 9.0–12.0% 12.0–15.0%  15.0%