1. Darwinian Evolution

2. Charles Darwin

3. H.M.S. Beagle
Naturalist???

4. Patterns of Diversity
Why do so many organisms seem so well suited to surviving and reproducing in a given environment?
Why do similar environments on different continents have different animals?

5. Living Organisms and Fossils
Why do organisms become extinct?
How are extinct organisms related to extant organisms?

6. Galapagos Islands
Why are there so many different forms of the same animals? Why do these forms differ from others found around the world?

7. The Journey Home
Why is there so much variation between organisms on different islands?
Why is there so much variation between organisms on the islands and organisms on South America?

8. The Inspiration of Geologists
James Hutton
Charles Lyell

9. Geology Inspiration

10. The Original Evolutionist
Jean-Baptiste Lamarck

11. Lamarck Example

12. The Economist Viewpoint
Thomas Malthus

13. The Economist Contribution

14. The Competition
Alfred Russel Wallace

15. Natural Variation

16. Selective Breeding

17. Natural Selection
The process in which the most fit organism survives and reproduces better than other less fit organisms
Possess adaptations that provide them with a reproductive advantage over other organisms

18. Are Adaptations Perfect?

19. Geographic Distribution of Species
Kaibab Squirrel
 North Rim of Grand
Canyon
Albert’s Squirrel
 South Rim of Grand
Canyon

20. Darwin’s Theory Variation Exists in Nature
More Offspring are produced than can survive – Some will not reproduce
Resources are limited and competition will ensue for these resources

21. Darwin’s Logic
Each organism possesses traits that either help or hinder it in this competition for resources
Those best suited to survive and reproduce in a given environment will survive and reproduce and pass on their genes

22. Darwin’s Logic
Species change over time and new traits and new species will arise
Today's species have descended from ancestors but with modifications
All organisms are united in a single tree of life by common descent

23. Homologous Structures
Indicates evolutionary relatedness

24. Analogous Structures

25. Convergent Evolution

26. Embryonic Similarities

27. Evolution and Genetics
Darwin’s Disadvantage…

28. Populations and Gene Pools
What is a gene pool?
Relative Frequency of an allele?
Example: Tasting PTC paper
In our survey – 85% could taste paper, 15% could not
Tasting paper is a dominant trait (25%TT or 60%Tt)
Not Tasting is a recessive trait (15%tt)
This would mean that 55% of the alleles for this trait are dominant (T) and 45% are recessive (t)

29. Sources of Genetic Variation
Mutations – Can change allelic frequencies
Silent vs. Expressed mutations
Gene Shuffling – Does not change allelic frequencies
Independent Assortment of Alleles
Crossing Over
But why is variation important in terms of evolution?

31. Forms of Selection
Variation typically exists in a population and when graphed, this variation typically takes on the shape of a bell curve
Selection can change the position of this curve in three different ways

32. Directional Selection
Definition:
Examples:
Darwin’s Finchs
Guppies and Coloration

33. Stabilizing Selection
Definition:
Example:
Weight of human infants at birth
Dalmatians and spots

34. ***Can lead to speciation***
Disruptive Selection
Definition:
***Can lead to speciation***

37. Changes in Allelic Frequencies
Genetic Drift – Change in the allelic frequencies of a population by chance
Typically affects smaller populations. Why?
Bean Example
Examples of Drift
Founder effect
Bottleneck effect

38. Founder Effect
Definition:
Example: Amish + Polydactyly

39. Bottleneck Effect
Definition:
Examples: Humans, Cheetahs

40. Evolution Vs. Genetic Equilibrium
Genetic Equilibrium – No changes in allelic frequencies within a population
But under what conditions does genetic equilibrium take place???

41. Hardy-Weinberg Principle
Genetic equilibrium will occur as long as the following criteria are met.
Random mating among members of population
Large population size
No gene flow (immigration or emigration)
No mutations
No natural selection

42. Speciation Species Definitions:
Anatomical –
Biological –
Evolutionary –
All species definitions have their benefits and limitations
Take home message – We do not have a definition that is valid for all situations

43. Speciation – The Process
In order for speciation to occur, there must be a disruption in the gene pool
2 sub-sets of the population must become isolated and begin to evolve separately from one another
Large Population
Sub-pop A
Sub-pop B

44. Types of Isolation Behavioral Isolation –
Example: Eastern and Western Meadowlarks
Other example: Fireflies

45. Types of Isolation Geographic Isolation –
Example: Abert Squirrel and Kaibab Squirrel
Other example: Mammal + Monotreme evolution

47. Types of Isolation Temporal Isolation –
Example: Orchids reproduce at different times
Other Example: Palm trees

48. How Rapid is Speciation
Early Beliefs:

49. How Rapid is Speciation
Stephen Jay Gould – Punctuated Equilibrium

50. But how does rapid change occur?
Cumulative Selection
Silent genes are expressed
Master Control Genes – Hox genes
Mutations at different times during development

51. Hox Genes

52. Hox genes and evolution