1. Oklahoma City Community College
Evolution, Part II
BIO 2215
Oklahoma City Community College
Dennis Anderson

2. Major Elements Of Life
Carbon
Hydrogen
Oxygen
Nitrogen C H O N

3. Chemical Evolution H O C H O H N H C Carbohydrates Fatty Acids
Simple Molecules
More Complex Molecules
Carbohydrates
Fatty Acids
Amino Acids H O C H O H N H C

4. Carbohydrates

5. Fatty Acids

6. Amino Acids

7. Figure 02.12

8. Proteinoid Microspheres
Similar to protocells
Protocells
Reproduce
Natural selection favored those with the most efficient replicating systems
RNA
DNA

9. Cyanobacteria Photosynthesis Carbon Dioxide + Water = Glucose + Oxygen
Produce oxygen
Produce carbohydrates
Carbon Dioxide + Water = Glucose + Oxygen

11. Microevolution Change in allele frequency of a population
Populations evolve, individuals do not

12. Terms Allele Dominant allele Recessive allele Homozygous Heterozygous
Member of a paired gene
Dominant allele
Allele that is expressed when combined with a recessive allele
Recessive allele
Allele that is NOT expressed when combined with a dominant allele
Homozygous
Both alleles the same, AA or aa
Heterozygous
Alleles are different, Aa

13. Terms Codominance Gene Pool Both alleles are dominant, AB blood type
All the alleles in a population

14. Math Explains Allele Frequencies
p + q = 1
p = percent of dominant alleles in a population
q = percent of recessive alleles in a population
If 70% of alleles in a population are dominant then 30% must be recessive

15. Genotype Frequencies Square the equation p + q = 1 p2 + 2pq + q2 = 1
Correlation between genotypes and variables in the equation are:
p2 = AA
2pq = Aa
q2 = aa

16. Hardy-Weinberg Equations
p + q = 1
Frequency of dominant alleles plus frequency of recessive alleles is 100% ( or 1)
p2 + 2pq + q2 = 1
AA plus 2Aa plus aa add up to 100% (or 1)
Applies to populations that are not changing
They are in equilibrium

17. Hardy-Weinberg Example
Normal pigmentation (not albino) = A
Albinism recessive = a
AA = (p2) = normal
Aa = (2pq) = normal
aa = (q2) = Albinism
1 in 20,000 people have albinism
aa = 1/20,000 =
a = 1/ =

18. First Equation p + q = 1 p + 0.00707 = 1 p = 1- q = .9929
p is the frequency of the dominant allele, A
q is the frequency of the recessive allele a
p = 1
p = 1- q = .9929

19. Second Equation p2 + 2pq + q2 = 1 p2 = AA 2pq = Aa q2 = aa
.9929 x = .9858
2pq = Aa
2 x x = .0140
q2 = aa
.00005
= or 1

20. Cystic Fibrosis Cystic fibrosis affects 1 in 2000 white Americans
Cystic fibrosis is recessive = cc
1 in 2000 = 1/2000 = .0005
q2 = .0005
What is q?

21. Value of q q is the square root of q2 q2 = .0005
What is p?

22. Value of p p + q = 1 Since q = .022 Then p = .978 (1-.022)
What are the values for p2 and 2pq?

23. Values for p2 and 2pq P2 = pxp =.978 x .978 = .956
2pq = 2 x .978 x . 22 = .043
4.3% of population are carriers for cystic fibrosis

24. Problem
Jack and Jill are expecting a baby. What is the chance the baby will have cystic fibrosis?

25. Solution The chance of Jack being a carrier is .043
The chance of Jill being a carrier is .043
The chance of two carriers producing a child with a recessive trait is .25
.043 x .043 x .25 = 1/2000

26. Practical Application of Hardy-Weinberg Equations
If you know the frequency of the recessive phenotype (aa) you can calculate the percent of the population that are carriers (Aa) and that are AA.

27. Populations are rarely in Hardy-Weinberg equilibrium
Most populations are evolving
Factors that cause allele frequencies to change
Nonrandom mating
Genetic drift
Gene flow
Mutation
Natural selection

28. Nonrandom Mating Most people choose their mates based on
Physical appearance
Ethnic background
Intelligence
Shared interests
One-third of marriages are between people born less than 10 miles apart

29. Religious & Cultural Influences
Many people will only marry within their own religion or culture
Consanguineous marriages increase risk of birth defects by 2.5 times

30. Hopi Indians Albinos stay in village with woman
Cannot tolerate the sun
Albinos have more opportunity to mate with females
1/200 Hopi Indians are albino
1/8 are carriers

31. Genetic Drift
Change in gene frequency when small a group of individuals leave or are separated from a larger population
Founder Effect
Bottleneck

32. Founder Effect 10 people leave to found a new population
10% with A allele
Original Population
1% has allele A 10
Founders
10 people leave to found a new population
1 of the founders has allele A
10% of new population will have allele A

33. Ellis-van Creveld Syndrome
Dwarfism
Extra fingers
Heart defects
High frequency in Amish population of Pennsylvania
A founder of the population had allele for the syndrome

34. Bottleneck Population almost dies out
Survivors genes are at a higher frequency in the descendants than the original population

35. Cheetah Bottleneck 2 major bottlenecks
10,000 years ago
1800’s
Present cheetah are more alike genetically than inbred lab mice

36. Gene Flow When genes move from one population to another
Genes flow between the two populations below
OKC
Dallas

37. Gene Flow Can change the frequency of genes in a population
If gene flow stops for a long period of time the two populations may change enough from each other to become new species.

38. No Gene Flow

39. Mutations Introduces new alleles into a population
Most mutations are lethal
Mutation for no heart would be lethal
Some mutations are beneficial
Block infection of HIV

40. Beneficial Mutation
Mutation for albinism beneficial for bears who live on the ice and snow
Polar bears were once part of a population of brown & black bears
Now polar bears are a separate species

41. Natural Selection
Some individuals are more likely to survive and pass on their genes than others
Nature selects against gene for black fur in the arctic
Black fur does not enable bears in that environment to survive as well
Nature selects against gene for white fur in Oklahoma
White fur is not as advantageous in Oklahoma

42. Tuberculosis Number 1 killer in 1900
Antibiotics decreased cases dramatically
1980 very few cases
Bacterium that causes TB is constantly mutating
Mutant strains resistant to antibiotics are naturally selected to survive

43. Evolution of Tuberculosis
Cases of TB
1900
1980
2000

44. Sickle Cell Anemia Frequency
Sickle cell anemia is most common in parts of Africa with malaria
Carriers who live in an environment with malaria have an advantage
Immune to malaria

45. Why is the frequency of sickle cell anemia lower in the USA population of Blacks than African populations from which they originated?
There is no selective advantage for the s allele in an environment with no malaria
The frequency of the s allele in the USA Black population has dropped significantly in the last 300 years.

46. Stabilizing Selection
Average value selected for
Extreme values selected against

47. Directional Selection
Favors values above or below average
Population will shift to the favored value

48. Disruptive Selection Extreme traits are both favored
Birds with small bills and large bills are better feeders
In a specific enrironment

49. Macroevolution
Evolution that results in new species

50. Allopatric Speciation
A barrier separates a population into two subpopulations
There is no gene flow between the two populations
Each population changes with time
Changes result in new species.

51. Sympatric Speciation
Different individuals occupy different parts of the environment
They breed in the areas they occupy

52. Convergent Evolution
Whales are mammals
Evolved a fish like body

53. Divergent Evolution
Mammal
Reptile
Bird

54. Coevolution

55. Parallel Evolution

56. Gradualism or Punctuated Equilibrium

57. The End