1. How Populations Evolve

2. Historical Theories Anaximander (~2500 yrs ago) Aristotle Georges Buffon (1700’s) Jean Baptist Lemark (late 1700’s - early1800’s) Erasmus Darwin

3. Charles Darwin 18591874

4. Voyage of the HMS Beagle

5. On the Origin of Species… Descent With Modification By means of Natural Selection

6. Support for Descent with Modification Biogeography Fossil Record Molecular Biology, Biochemistry, Cell Biology Comparative Anatomy

7. Homology of Structures

8. More Support Embryology Molecular Biology

9. How Did Darwin Come Up With His Ideas? Scientific Method Key observations –All species tend to produce excessive amounts of offspring (Thomas Malthus) –Individuals in a population vary –Many of the varying traits are passed from 1 generation to the next

10. Recap Limited resources Overproduction of offspring Heritable individual variation –Therefore, survival depends partly on inherited features

11. Darwin’s Theory of Evolution In a varied population, individuals whose inherited characters best adapt them to the environment are more likely to survive and reproduce. Therefore, they tend to leave more offspring than less fit individuals. Natural Selection is mechanism –Reproduction (differential) is Key

12. Natural Selection

13. Examples of Natural Selection English Peppered Moths

14. Artificial Selection

15. Population Genetics Modern Synthesis Species concept –Species = a group of populations whose individuals have the potential to: Interbreed Produce fertile offspring

16. Micro-Evolution Changes in the numbers (frequency) of alleles in a population Gene pool –All alleles of each gene in all individuals Ex. Peppered Moth –Before pollution, light allele color dominant (higher frequency) –After change, dark allele dominant

17. Gene Frequencies

18. Hardy-Weinberg Equilibrium Frequency of alleles in a stable population will not change over time –Very large population –Population is isolated –Mutations don’t alter gene pool –Random mating –All individuals are equal in reproductive success In reality, this never happens

19. Agents of Change Genetic Drift –Bottle neck affect

20. Bottle Neck Affect

21. Agents of Change Genetic Drift –Bottle neck affect –Founder affect Gene Flow

22. Agents of Change Genetic Drift –Bottle neck affect –Founder affect Gene Flow Mutation

23. Agents of Change Genetic Drift –Bottle neck affect –Founder affect Gene Flow Mutation Non Random Mating Natural Selection

25. Variation Traits Morphs -Polymorphism Geographic variation -Clines Natural Selection acts on variation

26. Variation Traits Morphs -Polymorphism Geographic variation -Clines Natural Selection acts on variation

27. Polymorphism in Snakes

28. Types of Selection

29. Speciation Speciation = evolution of a new species –Isolation often leads to speciation Barriers between organisms or populations Division is often not precise –Line gets blurry –Where do you draw the line when populations overlap?

30. Isolation Geogrphic isolation = Physical barriers –Valley, mountain range, river, ocean, etc. Reproductive Barriers –Separated by when they happen Prezygotic barriers = before fertilization Post zygotic = after fertilization

31. Geographic Isolation

32. Prezygotic Barriers Temporal isolation Habitat isolation Behavioral isolation Mechanical isolation Gametic isolation

33. Booby courtship behavior

34. Postzygotic Barriers Hybrid inviability Hybrid sterility Hybrid breakdown

35. Horse Donkey Mule

36. Types of Speciation Allopatric speciation –Population becomes cut off from other populations Becomes an isolated gene pool Often the initial event is geographic event –Isolated population often evolves in different direction

37. Types of Speciation Adaptive radiation –Development of many new species from a common ancestor introduced into a new and diverse environment –Very common on islands Islands must be colonized from the outside Darwins finches Hawai’ian honeycreapers

38. Honeycreapers

39. Adaptive Radiation

40. Types of Speciation Sympatric speciation –Speciation within a continuous range or area –Enough genetic change on either end of a large population range –Accidents in meiosis Primarily in plants

41. Selection & Speciation

42. Evolutionary Theories