1. Understanding the mechanisms of evolution: natural selection and genetic drift
Dr. Timothy Greives
Context: this unit fits within a larger unit focused on evolutionary mechanisms; students will have already learned

2. Evolution: Change over time
We want to try to understand how this change occurs in nature and how variation affects this change.
Lazuli Bunting
Indigo Bunting ?

3. Introduction Brief introduction to concepts and terms
Evolution: Change over time
Biological Evolution: Change frequency of heritable traits over time.
Genotype: An individuals set of genes determining a trait of interest (phenotype)
Phenotype: The observed trait of interest.
Phenotype is influenced by both the genotype and environment.
Selection: A certain trait that influences reproductive success and survival (= total number of lifetime offspring)

4. Artificial selection
Humans choose which trait to favor and breed individuals displaying those traits  increasing the total number of offspring in next generation.
Wild tomato found in South America
First cultivated by Native Americans
Size influenced in part by changes in a single gene (fw2.2) - which encodes protein that represses cell division

5. Artificial selection
Darwin studied the mechanism of evolution under domestication

6. Natural selection
Individuals that are able to survive to produce more offspring will have higher fitness
Instead of humans choosing the traits favored, nature will choose.

7. Evolution by (natural) selection

8. RE-Introduction
Evolution:
Biological Evolution:
Genotype:
Phenotype:

9. Experimental study system
Simple model organisms
Controlled environments
Use the organism M&M to demonstrate Evolution

10. The elusive POISONOUS M&M
Two color phenotypes of M&M’s
Reproduces asexually by fission

11. M&M fission

12. M&M fission

13. Reproduction by fission in real life

14. Please read through the activity instruction sheet silently.

15. Questions?

16. Please proceed through steps 1-4

17. Example of data sheets and graphs
Group: __________________________
Date: _____________________
Generation
Number of orange M & M's
Number of blue M & M's
Percentage of orange M & M's 10 50 1 4 2 7 3 5

18. Part II
Form hypotheses for abundance of orange M&M’s after introduction of a chocovoire.

19. Please complete activity

20. Evolution by Natural Selection in the Galapagos

21. Want to learn more about the finches?

22. Darwin’s finches “vampire finch” South America
Darwin first noticed while on the Beagle ( )
Grassquit colonized the islands from SA or CA 2.3 mya
Different bills with different diets
A few finches have managed to colonize these islands far from the South American continent. Their descendants have diversified to eat different items: different kinds of insects and seeds. This specialization can be seen in their beaks. Eventually birds that ate a specific kind of food started to mate more with each other than with other birds that ate other kinds of foods and they became separate species.
Galapagos

23. Huntington’s Disease

24. Frequency of Huntington’s Disease
Magazi et al South African Medical Journal
Greeff, JM Annals of Human Genetics
Hayden et al South African Medical Journal

26. ‪

27. Frequency of Huntington’s Disease
Magazi et al South African Medical Journal
Greeff, JM Annals of Human Genetics
Hayden et al South African Medical Journal

28. Huntington’s disease discussion
Form hypotheses – why is prevelance so much higher in the Afrakaner Dutch descendents?
Discuss hypotheses

30. Please read through the activity instruction sheet silently.

31. Questions?

32. Please proceed through steps 1-4

33. Please complete activity

34. Following M&M exercise –
revisit hypothesis regarding prevalence of Huntington’s disease in Afrikaner population
Magazi et al South African Medical Journal
Greeff, JM Annals of Human Genetics
Hayden et al South African Medical Journal

35. Conservation case study

36. Conservation case study
Cape buffalo (Syncerus caffer caffer)
Historically widespread and panmictic
Currently confined to protected areas
Isolation of populations
How might this affect genetic diversity?

37. Heller et al. 2010. Molecular Ecology. 19:1324-1334

39. What is wrong with the statement ‘survival of the fittest’?

40. Darwin’s finches
We can see how the different species of ground finches are specialized to eat different sized seeds. Could we see how selection may have driven this differentiation by looking a seed size preferences with in one species?

41. Diversity in traits Study skins of birds that have different diets.
-Can they make hypotheses about diet based on their observation of beak size, other features?