1. If having a widow’s peak has no advantage or disadvantage then why do the allele frequencies change?

2. More Than Natural Selection

3. Learning Objectives
List the two main types of evolution and give examples of each
List the four types of microevolution, give examples of each and compare and contrast them
Calculate the allele frequencies of a population

4. Review
Turn to a partner and tell them 3 big ideas you learned last class!

5. Review What is an allele?
What happens to alleles if evolution is occurring?
What are single-gene traits?
What are polygenic traits?

6. Polygenic Traits and Evolution
Polygenic traits produce a normal distribution (bell curve) of types. Natural selection acts on this distribution and alters it.

7. Types of Natural Selection
Directional selection
Stabilizing selection
Disruptive selection

8. Directional Selection

9. Directional Selection
Natural selection acts on one extreme of a trait. One extreme is less fit than the other. The distribution of the trait shifts from left to right or from right to left.

10. Examples?

11. Stabilizing Selection

12. Stabilizing Selection
Natural selection acts on both extremes of a trait. The extremes are less successful. The middle phenotype is most successful. The distribution becomes narrower.

13. Examples?

14. Disruptive Selection

15. Disruptive Selection
Natural selection acts on the midpoint of a trait. The middle phenotype is least successful. Both extremes are successful. The distribution separates into two peaks.

16. Examples?

17. Darwin’s Finches
Some of Darwin’s finches ate seeds. Polygenic trait: beak size and shape. How could they evolve in a Directional way? Stabilizing? Disruptive?

18. Evolution Stories Include: Polygenic trait Environmental pressure
Change in frequency of alleles
One of the types of natural selection

19. Once you are done: Find two other groups Listen to their stories
Guess which type of natural selection it is

20. Jigsaw! Your mission is to become an expert on an article.
Read the article, highlight important parts
Talk about the article in your “expert” group and analyze it
Share your new knowledge with your group

21. Jigsaw 1) Get in a group of 3 and get 3 packets
2) Decide who is responsible for each one
3) Read your packet and answer questions
4) Get together with same article group
5) Go back to original 3 and share

22. Questions Is it a single-gene or polygenic trait?
Do you think it increases the animals fitness? How?
What strategies or techniques did the researchers use to study the trait?
What is the next step in this research?
Do you think this research is important? Not important? Why?

23. Answers?

24. Types of Evolution
Microevolution: change in the allele frequencies of a population. e.g. color change in a group of beetles Macroevolution: evolution on a huge scale. e.g. Dinosaurs to birds

25. Dinosaur to Archaeopteryx to Kiwi
Macroevolution – evolution of a new group (birds).

26. Examples? Microevolution? Macroevolution? Gonorrhea? Fish? Plants?
All three were microevolution examples.

27. Microevolution Can lead to new species.
Species: a reproductively isolated group of animals.
The small changes of microevolution can add up and cause macroevolution.

28. Species
Horse and donkey can mate and produce a mule (middle). Mules are infertile. So donkeys and horses are separate species.

29. Types of microevolution
Natural Selection (includes sexual selection)
Mutation
Gene Flow
Genetic Drift

30. Mutation
Remember: evolution is the change in relative frequency of alleles in a population. Mutation introduces new types of alleles which means frequencies are changing.

31. Mutation
Generation 1 Generation 2 10 grey squirrels 19 grey squirrels 1 black squirrel freq. of grey allele = 1 freq. of grey allele = 0.95 freq. of black allele = 0.05 A new allele appears in the next generation so the allele frequencies change.

32. Mutation
Note: allele mutations occur in sex cells. They show up in the next generation.
You will not get a mutant allele. However if you put your laptop on your lap too long you might have a kid with a mutant allele.
(Please do not try for this).

33. Examples?
Gonorrhea

34. Mutation
Remember: some mutations are good, some bad, some have no effect. If a mutation has a positive or negative effect natural selection may act on it.

35. Mutation
What do you think will happen to a mutant allele if it has a major positive effect? A major negative effect? Little to no effect?

36. Sickle Cell Anemia
An example of a mutation acted on by natural selection.

37. Gene Flow
When individuals migrate in or out of a population they can introduce or remove new alleles by reproduction.

38. Gene Flow
When new alleles are introduced by reproduction the relative frequencies change and the population evolves. When alleles leave the population (individuals with those alleles no longer reproduce) the population evolves. Alleles are entering and leaving the gene pool.

39. Gene Flow This can be caused by events such as:
animals blown or washed out to islands or new areas
breakdown of previous barriers (removing a dam or a rockslide clearing a path between valleys)
or just animals traveling

40. Examples?
Pollen can travel huge distances, by wind or by insect and introduce new alleles through reproduction.

41. Gene Flow
Gene flow can be prevented by geographic features that isolate populations.
E.g. oceans, mountain ranges

42. Genetic Drift
Allele frequencies can change by chance.

43. Genetic Drift
What happens if you step on an ant hill? Or a flood or forest fire goes through a valley?

44. Genetic Drift
Some individuals die and some survive, but it is due to chance, not fitness.

45. Genetic Drift
It has the largest effect in small populations. Generation 1 Fire kills 4 Generation 2 white rabbits 5 black rabbits 10 black rabbits 4 white rabbit An allele completely disappeared by chance!

46. Genetic Drift
Large populations are not as affected. Generation 1 Fire kills 4 Generation 2 white rabbits 50 black rabbits 100 black rabbits 40 white rabbit 72 white rabbits Black = 0.56 Black = 0.58 White = 0.44 White = 0.42

47. Genetic Drift
Because it occurs by chance it means even mutations with no effect or mildly negative effects can increase in frequency.
Unless a trait is very beneficial or has very negative effects its alleles will likely stay in the population.
In a small population genetic drift could mean MOST animals do NOT have high fitness.

48. Examples?
Have you ever unknowingly caused genetic drift?

49. Types of Evolution Lab
Work with a partner or group of 3 (there are 10 dice, so if you have an app you could use that).
Fill out your own lab
Paper colored squares at front desk (you may need more or less than 20)

50. Human Evolution

51. Answer the Questions What is the name of our species?
When did our species evolve? Where?
Name at least 3 related species and list their derived and ancestral traits.
Why were humans successful while other species died off?
Who are the hobbits?
What is some of the evidence for human evolution? Find 3 examples and explain them.

52. Origin of Life
Some extra worksheets at side!

53. For homework:
Watch tv! Watch movies! Go online! Look for references to evolution. 1) What are they saying? 2) Is it accurate? A minimum of 2, write them down and bring to class.