1 / 13

The Evolution of Populations

Pops. The Evolution of Populations. Groupings. Species Pops of orgs that may interbreed to produce fertile offspring Population Local group of orgs of one species Evolution = change in the genetic makeup (allele frequencies) of a population. Hardy-Weinberg Conditions.

lida
Download Presentation

The Evolution of Populations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Pops The Evolution of Populations

  2. Groupings • Species • Pops of orgs that may interbreed to produce fertile offspring • Population • Local group of orgs of one species • Evolution = change in the genetic makeup (allele frequencies) of a population

  3. Hardy-Weinberg Conditions • Hypothetical conditions that must exist in a population for no evolution to occur

  4. Population Characteristics Hinder Evolution (Hardy-Weinberg Conditions) Infinitely Large Random Mating Equal Survival Isolation No mutations Help Evolution (Natural Conditions) Small  Genetic Drift Natural Selection Natural Selection Gene Flow Mutations POPULATION SIZE MATE SELECTION VARIATION OF ADAPTIVENESS INTERACTION W/ OTHER POPS DNA CHANGES

  5. Genetic Drift • Random fluctuations in allele frequencies • Example: • 2 red, 2 blue orgs seek shelter • 50% survive. All are red • Blues eliminated by chance (17%) • 4 red, 4 blue head for shelter • 50% survive. All are red • Blues eliminated by chance (1.4%)

  6. Genetic Drift • Bottleneck Effect • Catastrophe cuts pop size • Decreased variety of traits • Altered allele frequencies • Genetic drift more likely

  7. Genetic Drift • Founder Effect • Small group emigrates to new habitat 

  8. Gene Flow • Introduction of new traits through immigration • May be beneficial or insignificant • New traits  altered trait frequencies 

  9. Quantifying Evolution Gene Pool • entire set of alleles present in the population Evolution • change in frequency of alleles in the population p = frequency of one allele (usu. dom.) q = frequency of another allele (usu. Rec.) p + q = 1

  10. Quantifying Evolution • p2 = frequency of homozygous dominants • q2 = frequency of homozygous recessives • 2pq = frequency of heterozygotes p + q = 1 p2+ 2pq + q2 = 1

  11. Quantifying Evolution Symbolized as “2pq” Symbolized as “p2” Symbolized as “q2” Symbolized as “p” Symbolized as “q”

  12. Hardy-Weinberg Probs • In Drosophila, the allele for normal wings is dominant over the allele for vestigial wings. In a pop of 1000, 490 have vestigial wings. How many individuals would you expect to be homozygous dominant? Heterozygous? • q2 = .49 • q = .7 • p = .3 • p2 = .09 • 2pq = .42

  13. Hardy-Weinberg Probs • In the US, 64% of people have free earlobes. What is the frequency of the dominant allele? • p2 + 2pq = .64 • q2 = .36 • q = .6 • p = .4

More Related