1. Evolution of Populations
Genes & Variation--What causes Genetic Variation in Populations?

2. Mutations
Gene Shuffling
Crossing Over

4. Gene Pools and Allele Frequencies
What is a gene pool?
(All of the genes and information from all members of a particular species)
What are Allele Frequencies?
(How many times that allele occurs in the gene pool---eg. Black fur B = 40%)

5. Sources of Genetic Variation
Mutations
Gene Shuffling chromosomes can produce 8.4 million different combinations of genes
Crossing Over -- Further, “Shufffles the deck” Producing more combinations

6. New Combinations of Alleles

7. Single Genes & Polygenic Traits
Single Gene Traits
AA, Aa, aa
Polygenic Traits
AABBCC, AaBbCc
(3 Genes) >

8. Natural Selection on Single gene Traits
Can Lead to changes in the Allele Frequencies and
consequently----> Evolution
Example--Black and brown lizards
Red (mutation) doesn’t survive as well on a dark background

10. Natural Selection on Polygenic traits
Can affect the distributions of phenotypes in 3 ways---
1) Directional selection
2) Stabilizing selection
3) disruptive selection

11. Stabilizing Selection -->Selects for the average form

12. Directional Selection -->Selects for an extreme

13. Diversifying Selection--Selects for both extremes

14. Natural Selection on Single Gene Traits

15. Genetic Drift

16. Genetic Drift in The Amish

17. Example of Genetic Drift
An example is the frequency of total color-blindness among the inhabitants of Pingelap, an island in Micronesia. In approximately 1775, a typhoon reduced the population of the island to only 20. Among survivors, one of them was heterozygous for achromatopsia.

18. After few generations, the prevalence of achromatopsia is 5% of population and 30% as carriers (by comparison, in the United States, only 0.003% of the population has complete achromatopsia.

20. Amish polydactyl (6 fingered) Achondroplastic Dwarf

21. Evolution vs. Genetic Equilibrium
Evolution = Genetic Change
What does Genetic Equilibrium = ?
NO CHANGE ! POPULATIONS WOULD STAY THE SAME, “IN EQUILIBRIUM”

22. Remember the Blue-footed Booby?

24. Hardy-Weinberg Equilibrium

25. Conditions for Equilibrium (Hardy--Weinberg)
What would the conditions have to be for no change? ie. No Evolution
1. No mutation
2. No natural selection
3. Large population
4. All members of the population breed

26. 5. Random mating
6. everyone produces the same number of offspring
7. no migration in or out of the population

27. Speciation

28. Isolating Mechanisms
GEOGRAPHIC
REPRODUCTIVE
BEHAVIORAL
TEMPORAL

29. GEOGRAPHIC ISOLATION
Leads to--> Reproductive Isolation

31. REPRODUCTIVE ISOLATION
Species can no longer reproduce with the, “New” species
Eg. 2 species of fruitflies
Guava or Banana?
The evolution of different mating location, mating time, or mating rituals:

32. TEMPORAL ISOLATION Mating at different times of the year Other frogs--
Green frogs--> April
Bullfrogs--> June

33. BEHAVIORAL ISOLATION Courtship rituals--(Dances, Flashes,)
Food preferences

34. Firefly--> Flashes

35. Misconception: “Natural selection gives organisms what they ‘need.’ ”