1. Population Genetics

2. The Gene Pool
Members of a species can interbreed & produce fertile offspring
Species have a shared gene pool
Gene pool – all of the alleles of all individuals in a population

3. The Gene Pool Different species do NOT exchange genes by interbreeding
Different species that interbreed often produce sterile or less viable offspring e.g. Mule

4. Populations A group of the same species living in an area
No two individuals are exactly alike (variations)
More Fit individuals survive & pass on their traits

5. Speciation Formation of new species
One species may split into 2 or more species
A species may evolve into a new species
Requires very long periods of time

6. Modern Evolutionary Thought

7. Modern Synthesis Theory
Combines Darwinian selection and Mendelian inheritance
Population genetics - study of genetic variation within a population
Emphasis on quantitative characters (height, size …)

8. Charles Darwin
Collected specimens During journey on the HMS Beagle Wrote about conclusions in the Origin of the Species

9. Darwin’s Finches of the Galapagos

11. Wallace’s Line
The Wallace Line or Wallace's Line is a faunal boundary line drawn in 1859 by the British naturalist Alfred Russel Wallace that separates the ecozones of Asia and Wallacea, a transitional zone between Asia and Australia.

12. Modern Synthesis Theory
1940s – comprehensive theory of evolution (Modern Synthesis Theory)
Introduced by Fisher & Wright & Haldane
Until then, many did not accept that Darwin’s theory of natural selection could drive evolution
S. Wright
Haldane

13. Sir Ronald A. Fisher
Statistician combined Mendel’s work and natural selection --also created many biostatistics used today

14. Sewall Wright
Geneticist used included selection in path analysis Founder of population genetics with Fisher and Haldane

15. Modern Synthesis Theory
TODAY’S theory on evolution
Recognizes that GENES are responsible for the inheritance of characteristics
Recognizes that POPULATIONS, not individuals, evolve due to natural selection & genetic drift
Recognizes that SPECIATION usually is due to the gradual accumulation of small genetic changes

16. Microevolution
Changes occur in gene pools due to mutation, natural selection, genetic drift, etc.
Gene pool changes cause more VARIATION in individuals in the population
This process is called MICROEVOLUTION
Example: Bacteria becoming unaffected by antibiotics (resistant)

17. Hardy-Weinberg Principle

18. The Hardy-Weinberg Principle
Used to describe a non-evolving population.
Shuffling of alleles by meiosis and random fertilization have no effect on the overall gene pool. 
 Natural populations are NOT expected to actually be in Hardy-Weinberg equilibrium.

19. The Hardy-Weinberg Principle
Deviation from Hardy-Weinberg equilibrium usually results in evolution
Understanding a non-evolving population, helps us to understand how evolution occurs
                        .

20. 5 Assumptions of the H-W Principle
Large population size - violation: small populations have fluctuations in allele frequencies (e.g., fire, storm).
No migration - violation: immigrants can change the frequency of an allele by bringing in new alleles to a population.
No net mutations - violation: if alleles change from one to another, this will change the frequency of those alleles

21. 5 Assumptions of the H-W Principle
Random mating - Violation: if certain traits are more desirable, then individuals with those traits will be selected and this will not allow for random mixing of alleles.
No natural selection - Violation: if some individuals survive and reproduce at a higher rate than others, then their offspring will carry those genes and the frequency will change for the next generation.

22. Traits Selected = non-Random Mating

23. The Hardy-Weinberg Principle
The gene pool of a NON-EVOLVING population remains CONSTANT over multiple generations (allele frequency doesn’t change)
The Hardy-Weinberg Equation: 
               1.0 = p2 + 2pq + q2
 Where:
p2 = frequency of AA genotype
2pq = frequency of Aa
q2 = frequency of aa genotype

24. The Hardy-Weinberg Principle
Determining the Allele Frequency using Hardy-Weinberg: 
              
1.0 = p + q
 Where:
p = frequency of A allele
q = frequency of a allele

25. Estimating allelic frequencies:
If one or more alleles are recessive, can’t distinguish between heterozygous and homozygous dominant individuals.
Use Hardy-Weinberg to calculate allele frequencies based on the number of homozygous recessive individuals.
If q2 = , then q = 0.065; p = 1 - q = 0.935
p2 = , 2pq =

26. Allele Frequencies Define Gene Pools
500 flowering plants
480 red flowers
20 white flowers
320 RR
160 Rr
20 rr
As there are 1000 copies of the genes for color,
the allele frequencies are (in both males and females):
320 x 2 (RR) x 1 (Rr) = 800 R; 800/1000 = 0.8 (80%) R
160 x 1 (Rr) + 20 x 2 (rr) = 200 r; 200/1000 = 0.2 (20%) r

29. Allele and Genotype Frequencies
Each diploid individual in the population has 2 copies of each gene. The allele frequency is the proportion of all the genes in the population that are a particular allele.
The genotype frequency of the proportion of a population that is a particular genotype.
For example: consider the MN blood group. In a certain population there are 60 MM individuals, 120 MN individuals, and 20 NN individuals, a total of 200 people.
The genotype frequency of MM is 60/200 = 0.3.
The genotype frequency of MN is 120/200 = 0.6
The genotype frequency of NN is 20/200 = 0.1

30. The genotype frequency of MM is 60/200 = 0. 3
The genotype frequency of MM is 60/200 = 0.3. The genotype frequency of MN is 120/200 = 0.6 The genotype frequency of NN is 20/200 = 0.1 The allele frequencies can be determined by adding the frequency of the homozygote to 1/2 the frequency of the heterozygote. The allele frequency of M is 0.3 (freq of MM) + 1/2 * 0.6 (freq of MN) = 0.6 The allele frequency of N is /2 * 0.6 = 0.4 Note that since there are only 2 alleles here, the frequency of N is 1 - freq(M).

31. Microevolution of Species

32. Causes of Microevolution
Genetic Drift
- the change in the gene pool of a small population due to chance
Natural Selection
- success in reproduction based on heritable traits results in selected alleles being passed to relatively more offspring (Darwinian inheritance)
- Cause ADAPTATION of Populations
Gene Flow
-is genetic exchange due to the migration of fertile individuals or gametes between populations

33. Causes of Microevolution
Mutation
a change in an organism’s DNA
Mutations can be transmitted in gametes to offspring
Non-random mating
- Mates are chosen on the basis of the best traits

34. Genetic Drift

35. Genetic Drift
Genetic drift is the random changes in allele frequencies. Genetic drift occurs in all populations, but it has a major effect on small populations.
For Darwin and the neo-Darwinians, selection was the only force that had a significant effect on evolution. More recently it has been recognized that random changes, genetic drift, can also significantly influence evolutionary change. It is thought that most major events occur in small isolated populations.

36. Factors that Cause Genetic Drift
Bottleneck Effect
a drastic reduction in population (volcanoes, earthquakes, landslides …)
Reduced genetic variation
Smaller population may not be able to adapt to new selection pressures
Founder Effect
occurs when a new colony is started by a few members of the original population
May lead to speciation

38. Loss of Genetic Variation
Cheetahs have little genetic variation in their gene pool
This can probably be attributed to a population bottleneck they experienced around 10,000 years ago, barely avoiding extinction at the end of the last ice age

40. Bottlenecks
Example: Pingalop atoll is an island in the South Pacific. A typhoon in 1780 killed all but 30 people. One of survivors was a man who was heterozygous for the recessive genetic disease achromatopsia. This condition caused complete color blindness. Today the island has about 2000 people on it, nearly all descended from these 30 survivors. About 10% of the population is homozygous for achromatopsia This implies an allele frequency of about 0.26.

41. Founder’s Effect

42. Founder Effect Example
Founder effect example: the Amish are a group descended from 30 Swiss founders who renounced technological progress. Most Amish mate within the group. One of the founders had Ellis-van Crevald syndrome, which causes short stature, extra fingers and toes, and heart defects. Today about 1 in 200 Amish are homozygous for this syndrome, which is very rare in the larger US population.
Note the effect inbreeding has here: the problem comes from this recessive condition becoming homozygous due to the mating of closely related people.

43. Modes of Natural Selection

44. Modes of Natural Selection
Directional Selection
Favors individuals at one end of the phenotypic range
Most common during times of environmental change or when moving to new habitats

45. Directional Selection

46. Disruptive selection Favors extremes over intermediate phenotypes
Occurs when environmental change favors an extreme phenotype

47. Disruptive Selection

48. Modes of Natural Selection
Stabilizing Selection
Favors intermediate over extreme phenotypes
Reduces variation and maintains the current average
Example: Human birth weight

50. Variations in Populations

51. Geographic Variations
Variation in a species due to climate or another geographical condition
Populations live in different locations
Example: Finches of Galapagos Islands & South America

53. Heterozygote Advantage
Favors heterozygotes (Aa)
Maintains both alleles (A,a) instead of removing less successful alleles from a population
Sickle cell anemia
> Homozygotes exhibit severe anemia, have abnormal blood cell shape, and usually die before reproductive age.
> Heterozygotes are less susceptible to malaria

54. Sickle Cell and Malaria

56. Other Sources of Variation
Mutations
In stable environments, mutations often result in little or no benefit to an organism, or are often harmful
Mutations are more beneficial (rare) in changing environments  (Example:  HIV resistance to antiviral drugs)
Genetic Recombination
source of most genetic differences between individuals in a population

57. Co-evolution
-- when changes in at least two species' genetic compositions reciprocally affect each other's evolution
-- a change in the genetic composition of one species (or group) in response to a genetic change in another.
-Often occurs between parasite & host and flowers & their pollinators, and predator and prey

58. Coevolution pollinators

61. Parasitic relationships