1. Chapter 23: The Evolution of Populations

2. Population Genetics
microevolution – change in genetic makeup of a population from generation to generation

3. macroevolution – evolutionary change above the species level

4. population – group of individuals of the same species living in the same area

5. gene pool – all the genes in a given population at a given time

6. allele frequency – proportion of an allele in a gene pool
p = dominant allele
q = recessive allele
f (p) = frequency of the dominant allele
f (q) = frequency of the recessive allele

8. Calculating allele frequency:

9. Genotype # of Individuals MM 1787 MN 3039 NN 1303 Total 6129
Genotypic frequencies MM
1787
MM = 1787/6129 = 29% MN
3039
MN = 3039/6129 = 50% NN
1303
NN = 1303/6129 = 21%
Total
6129

10. Hardy-Weinberg Theorem
helps measure changes in allele frequencies over time
provides an “ideal” population to use as a basis of comparison

11. Conditions for Hardy-Weinberg Equilibrium:
Large population
No gene flow
No mutations
Random mating
No natural selection
– hypothetical population that is not evolving
– rarely met in nature

12. Mutation and sexual recombination only sources of new variations
mutation – changes in nucleotide sequence in DNA

13. point mutations – change in one nucleotide

14. gene duplication – duplication of a chromosome segment

15. sexual recombination – crossing over, shuffling of genes during meiosis

16. Genetic Drift – change in allele frequencies due to chance
usually in smaller populations
reduces genetic variation

17. bottleneck effect –when a population has been dramatically reduced, and the gene pool is no longer reflective of the original population’s

18. Human actions can create a genetic bottleneck

19. founder effect – when a small number of individuals colonize a new area; new gene pool not reflective of original population

20. The Fugate family Kentucky's Troublesome Creek

21. gene flow – when a population gains or loses alleles
a movement of fertile individuals leaving/arriving
– a reduces differences between populations

22. genetic variation – heritable variations in a population

23. discrete characteristics – are all one discrete variety

24. quantitative characteristics – vary along a continuum, usually due to influence of two or more genes

26. average heterozygosity – measure of polymorphism in a population

27. geographic variation – difference in variation between population subgroups in different areas

28. cline – a graded change in a trait along a geographic axis

29. (the more offspring that you have that survive = more fit you are)
Evolutionary Fitness
fitness – contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals
(the more offspring that you have that survive = more fit you are)

30. relative fitness – fitness of a particular genotype

31. Types of selection
directional selection – shift toward a favorable variation

32. disruptive selection
– favors the extremes

33. stabilizing selection
– favors the mean

34. Heterozygous Advantage – when individuals heterozygous
Recessive allele is maintained in the population

35. Example: sickle-cell anemia
prevelence of malaria sickle-cell disease

36. Sexual selection – a natural selection for mating success

37. Sexual dimorphism – differences between the sexes in secondary sexual characteristics

38. Not necessarily better adaptations; example – mane on lion very hot, feathers on peacock very “expensive” to make

39. Common misconceptions:
Natural selection acts on phenotype, not genotype!
Natural selection does not create more perfect organisms! (what is perfect in one environment may not be perfect in another)