1. Population Genetics
Chapter 16 & 17

2. Vocabulary
Population- a group of individuals living in the same area that breed with each other.

3. Gene Pool
Gene pool- combination of genetic information from all of the individuals in the population.

4. What is Genetic Variation?
Differences in alleles of genes
Provides the raw material for natural selection
Genetic variation occurs among populations

5. Sources of Genetic Variation
Mutations-
Changes in the DNA of the individual
If the mutation effects the individuals fitness it will effect the gene pool of the population
Gene Shuffling-
Occurs during the production of gametes
Each chromosome moves independently during meiosis
Crossing over

6. Relative Frequency
The number of times that an allele occurs in the gene pool.
Relative frequency has nothing to do with dominant and recessive
Evolution involves changes in populations over time 30 20

7. What is Evolution How is Evolution measured?
Any change over time in the relative frequencies of alleles in a population
It is populations not individual organisms that can evolve over time

8. Allele frequencies/ Gene pool
Change in relative frequency= evolution

9. Single Gene vs. Polygenic Traits
The number of phenotypes produced is based on the number of genes that control the trait
Controlled by 1 gene
produces 2 phenotypes
Traits that are controlled by 2 or more genes
more than 2 alleles for each trait

10. Natural Selection on Single-gene traits
Individuals either live or die based on their phenotype
A normally brown population of lizards experiences mutations that produce red and black lizards
What will happen to the population?
What if the red lizards stand out more?
What if the black lizards have an advantage over all other lizards?

11. Natural Selection on Single-gene traits
What do you expect the lizard population will look like by generation 50? Explain

12. Natural Selection on polygenic traits
When fitness varies natural selection can act
Three different ways that natural selection can affect the distribution of phenotypes
Directional Selection
Stabilizing Selection
Disruptive Selection

13. Directional Selection
What would cause this shift?
When individuals at one end of the curve have higher fitness
The range of phenotypes shifts as individuals fail to survive/reproduce

14. Stabilizing Selection
What causes the shift?
When individuals near the center of the curve have higher fitness then either end

15. Disruptive Selection What would cause the shift?
When individuals at either end of the curve have higher fitness then individuals near the middle
Natural selection works hardest on the intermediate type

16. Genetic Drift
Genetic Drift the random change in allele frequencies based on chance
Some individuals reproduce more times then others
Leave behind more offspring
Has nothing to do with natural selection

17. Genetic Drift
Relative frequencies move towards those that reproduce more times in the population
Eventually all the individuals in the population will have the same traits

18. Genetic Drift Genetic Drift is most common in small populations
In large populations there is a higher chance that individuals will find a mate
Genetic Drift leads to change in relative frequency and therefor evolution

19. Speciation
Diversity of Life

20. Speciation Formation of new species
Species: organisms that breed with one another and produce fertile offspring (share the same gene pool)
Caused by natural selection and chance events
Donkey
Horse
Mule

21. How does speciation happen
Shared gene pool
Genetic Change in 1 individual
Change spreads through the population through reproduction
Division/Isolation amongst the population
Population begins evolving independently

22. Reproductive Isolation
Division amongst the population
Population must become reproductively isolated for 2 new species to develop
Allows for mutations/ changes in the gene pool to happen independently
3 types of isolation mechanisms
Behavioral Isolation
Geographic Isolation
Temporal Isolation

23. Behavioral Isolation
Different behaviors stop the individuals from being attracted to one another
Different mating rituals
Song
Dance
Color pattern
Antler size

24. Geographic Isolation
Population becomes separated by a geographic barrier
River
Mountain
Bodies of water
Forests
The individuals cannot pass onto the other side of the barrier and therefore cannot mate

25. Founder Effect
A small group from a population branches off and forms a NEW population
Geographically isolated from the origninal
Individuals carry alleles in different relative frequencies then the original population

26. Human Influence on Geographic isolation
Man made structures create geographic isolation
Roads
Towns
River Dams

27. Temporal Isolation Reproductions times differ
Organisms reproduce at specific times of the day or year
Plants (morning vs. night)
Animals (spring vs. summer vs. fall vs. winter)

28. Patterns of Evolution
17-4

29. Microevolution Small changes in a species that build over time
Accounts for closely related species

30. Macroevolution Supports the idea of Common Decent
Large-scale evolutionary patterns and process that occur over long periods of time
Supports the idea of Common Decent

31. Punctuated Equilibrium
Patterns of long, stable periods interrupted by brief periods of more rapid change
100,0001,000,000 years
Changes come in spurts
Caused by
Geographic isolation
Migration
Mass extinctions

32. Gradualism
Small variations that are hard to notice over a short period of time
Variation takes place
slowly (gradually)

33. Gradualism vs. Punctuated Equilibrium

34. Extinction The end of a species or group of species
Natural selection causes extinction
Most common cause for extinction:
Species compete for limited resources
Environments change individuals can’t survive
Why is extinction necessary for evolution to continue?
video

35. Mass extinction
Mass extinction: many types of living things became extinct at the same time
A the end of the Paleozoic era many organisms died out
95% of the complex life in the oceans disappeared
Not all organisms disappeared
Reason for mass extinction
Collapsing environment
Caused by multiple factors

37. How did the extinction of the dinosaurs allow for the diversification of mammals?

38. Adaptive Radiation
A single species evolves into diverse forms that live in different ways

39. Convergent Evolution
Process in which unrelated organisms come to resemble each other (Analogous Structures)
“side effect” of adaptive radiation
Takes place among different species that live in similar ecological environments
Face similar environmental demands

40. Coevolution
The process where 2 species evolve in response to changes in each other
Evolutionary change in one organism induces change in the other
Flowers/pollinator
Predator/Prey

41. Hardy-Weinberg Principle
Genetic Equilibrium
Hardy-Weinberg Principle

42. Population Genetics
Evolution is the change in frequencies of alleles in the gene pool of a population
The gene pool has been shifted toward the “b” allele
Parent Generation
F1 offspring
Allele- B
92%
82%
Allele- b 8%
18%

43. Genetic Equilibrium
Genetic Equilibrium
The situation in which allele frequencies stay the same with each new generation
Parent Generation
F1 offspring
Allele- B
92%
Allele- b 8%
How likely is it that the allele frequencies will stay the same from one generation to the next?

44. Hardy-Weinberg principle
Allele frequencies in a population will stay constant unless one or more of the factors are violated
What are some conditions under which NO evolution will occur?

45. Maintaining equilibrium
Genetic Equilibrium:
Random mating
Large population
No movement into or out
No mutations
No natural selection
Each of these things can cause evolution to take place!

46. Random Mating
All individuals must have an equal opportunity to reproduce
In nature is mating completely random? Why or why not?

47. Large populations
Large populations decrease the chances of genetic drift taking place
Why is genetic drift not as common in large populations?

48. No movement into or out
When individuals move into a population or out of it, the gene pool will change

49. No mutations What role do mutations play in evolution?
Mutations introduce new alleles into the population

50. No natural selection
Natural selection gives one phenotype the advantage over the other

51. Real Life? Does the Hardy-Weinberg equilibrium exist in real life?
Random mating
Large population
No movement into or out
No mutations
No natural selection
Evolution is inevitable
In most populations evolution happens!