1. Monday, April 7 th Genetics of Populations

2. Population Genetics Vocab Population: A localized group of individuals belonging to the same species Species: A group of populations whose individuals have the potential to breed and produce fertile offspring

3. Which is which?

5. Population Genetics Vocab Gene pool: All of the genes in a population at any one time

6. How do populations change over time? GENOTYPE is inherited NOT the phenotype Mutations: A change in an organism’s DNA Original source of new alleles Mutation types: Lethal, Neutral, Beneficial

7. How do populations change over time? Individuals are selected, but populations evolve Evolution = a change in frequencies of alleles in the gene pool of a population

8. Evolutionary force? We are!

9. How do populations change over time? Relative Frequency: How often alleles are found in the pop. Genetic Equilibrium: When the allele frequency is unchanging EVOLUTION stops

10. What is the Hardy-Weinberg Principle? Serves as a model for a non-evolving population 5 CONDITIONS 1) Mutations are not occurring 2) Population is infinitely LARGE 3) No migration in/out of the population 4) Mating is totally random 5) Natural selection is not occurring

11. What is the Hardy-Weinberg Principle? Equation - under ideal conditions you could easily predict genotype frequencies from allele frequencies For two alleles (which we will call A and a), the Hardy-Weinberg equation is based on the binomial distribution: p 2 + 2pq + q 2 = 1 p = frequency of A q = frequency of a p + q = 1

12. What is the Hardy-Weinberg Principle? p 2 is the frequency of AA homozygotes 2pq is the frequency of Aa heterozygotes q 2 is the frequency of aa homozygotes H-W can be viewed as an extension of the Punnett square, using frequencies other than 0.5 for the gamete (allele) frequencies

13. What is the Chi-square test? Is used to compare OBSERVED data with data we would EXPECT Is there a significant difference between the expected frequencies and the observed frequencies in a population? Do the number of individuals that fall in each category differ significantly from the number you would expect?

14. What are the types of natural selection? 3 types of natural selection: 1. Directional Favors one extreme phenotype over the other Usually seen in environments that have changed over time Changes in weather, climate, or food availability

15. What are the types of natural selection? Example of DIRECTIONAL Darwin’s finches on the Galapagos Islands The beak length changed over time due to available food sources When there was a lack of insects to eat, finches with larger and deeper beaks survived because they could crack seeds Over time, as insects became more plentiful, directional selection favored finches with smaller and longer beaks.

16. Directional

17. What are the types of natural selection? 2. Diversifying or Disruptive Occurs when selection favors the extreme trait values over the intermediate trait The population is divided into 2 distinct groups Plays an important role in speciation

18. What are the types of natural selection? Example of Diversifying or Disruptive Peppered moths In rural areas, the peppered moths were almost all a very light color. These same moths were very dark in color in industrial areas. It seems that the darker colored moths survived predators in the industrial areas by blending in to the polluted surroundings.

19. Diversifying or Disruptive

20. What are the types of natural selection? 3. Stabilizing Occurs when selection favors the intermediate trait (the middle or average trait) over the extreme traits Ex: Siberian Huskies Strong leg muscles Heavier muscles would mean sinking in the snow Run slower pulling the sled

21. What are the types of natural selection? Example of Stabilizing Human birth weight is not only a polygenic trait, but it is also controlled by environmental factors Infants with average birth weight are more likely to survive than a baby that is too small or too large. The bell curve peaks at a birth weight that has the minimum death rate.

22. Stabilizing

24. What is Genetic Drift? Changes in the gene pool of a small population due to chance In each generation, some individuals (by chance) leave behind more descendents than others Based on LUCK, not healthier or better

25. Genetic drift reduces genetic variability & it doesn’t work to produce adaptations

26. What is the Bottle Neck Effect? Populations are reduced to small size for at least 1 generation & recover Reduces genetic variation Does not represent original population

28. Examples of bottle neck effect Cheetahs So little genetic variation, skin grafts from one to another do not trigger an immune response Elephant seals Around 30 members were alive in the 1890’s Tens of thousands today

29. Example of bottle neck effect

30. European Bison All alive today descended from a population of 12 More prone to diseases Increasing rates of male infertility

31. Example of bottle neck effect Florida Panthers One of the rarest mammals on Earth Total of 80 in the wild Crooked tails Heart defects Reproductive abnormalities

32. What is the Founder Effect? A couple of organisms become separated from a population A new colony is started by a few members of the original population All genetic variation is limited to those isolated individuals

33. What is the Founder Effect?

34. How do “new” species develop? Geographic isolation 2 populations are separated by geographic barriers; such as mountain ranges, rivers

35. How do “new” species develop? Behavioral isolation 2 populations are capable of interbreeding but have differences in courtship rituals

36. How do “new” species develop? Temporal isolation 2 or more species reproduce at different times

37. Dracula simia (monkey orchid), Orchis italica (naked man orchid), Habenaria radiata (white egret orchid) and Caleana major (flying duck orchid)