1. The Theory of Evolution

2. Earth’s History The Earth was formed about 4.6 billion years ago The Earth was formed about 4.6 billion years ago by 2.2 billion years ago, the Earth probably looked like it looks today by 2.2 billion years ago, the Earth probably looked like it looks today oxygen was not believed to be in abundant supply in Earth’s early atmosphere oxygen was not believed to be in abundant supply in Earth’s early atmosphere

3. Earth’s History oldest known cellular fossil (3.5 billion years old) traces back to a place in Australia oldest known cellular fossil (3.5 billion years old) traces back to a place in Australia - were probably cyanobacteria = photosynthetic unicellular prokaryotes - first prokaryotes were probably anaerobic – Why?

4. Earth’s History uniformitarianism = a principle that states the same geographical processes that occur today occurred in the past uniformitarianism = a principle that states the same geographical processes that occur today occurred in the past - these processes occur very slowly, requiring organisms to change as well (very slowly)

5. Uniformitariansim

6. Charles Darwin

7. did most of his research on the Galapagos Islands did most of his research on the Galapagos Islands

8. Charles Darwin - collected 13 similar but separate species of finches - collected 13 similar but separate species of finches - each had a distinct type of beak for feeding - overwhelming similarities showed they came from a common ancestor

9. Charles Darwin

12. Darwin’s Theories 1) New species descend from one or a few original types - similar organisms arise in the same geographic location 2) Species were modified and evolution occurred because of natural selection = organisms best suited for the environment survive better (or have higher fitness) and reproduce more successfully than others

13. Darwin’s Theories 3) The process of natural selection drives evolution 4) The environment “selects” the traits that will be increase a population - adaptation = when an organism becomes better suited for its environment

14. Evidence of Evolution 1) Homologous Structures = similar features that originated in a common ancestor ex) forelimbs of a cat, whale, bat, and human human - look different and vary in function, but very similar in skeletal structures very similar in skeletal structures - indicates they share a common ancestor ancestor

15. Homologous Structures

16. Evidence of Evolution 2) Analogous Structures = serve identical functions and look somewhat alike - ex) wing of a hummingbird and wing of a moth - indicates they show a remote ancestor but evolved independently and differently

17. Analogous Structures

18. Evidence of Evolution 3) Vestigial Structures = structures that are found in an organism but are not useful to them - were useful to a common ancestor - ex) human tailbone, appendix, tiny limb bones in snakes, pelvic bones in whales

19. Vestigial Structures

23. Types of Natural Selection - a population is the smallest unit in which evolution can occur - bell curve = a graph that illustrates that most members of a population show the average form a given measurable trait - only a few individuals will show the extremes of a trait

24. Bell Curve

25. Types of Natural Selection (cont) 1) Stabilizing Selection = individuals with the average form of a trait have higher fitness - the most common kind of selection - results in very similar morphology of a species

26. Stabilizing Selection

28. Types of Natural Selection (cont) 2) Directional Selection = individuals with the more extreme form of a trait have greater fitness than the average form

29. Directional Selection

31. Types of Natural Selection (cont) 3) Disruptive Selection = individuals with either extreme variation of a trait have greater fitness than individuals with the average form

32. Disruptive Selection

34. Types of Natural Selection (cont) 4) Sexual Selection = females tend to chose the males they mate with based on certain traits - the genes of successful reproducers, rather than those of merely successful survivors, are amplified through natural selection

35. Sexual Selection

38. New Species - speciation = the process of species formation - Speciation begins with isolation - 2 ways for this to occur

39. New Species (cont) 1) Geographic Isolation = the physical separation of members of a population - ex) fish in ponds in Death Valley - fish diverged enough to be considered separate species

40. Geographic Isolation – Death Valley

41. Geographic Isolation - Pupfish

42. New Species (cont) 2) Behavioral Isolation - ex) different mating times and calls of frogs reduce the chance of interbreeding among the different species

43. Behavioral Isolation - Frogs

44. Rates of Speciation 1) Gradualism = species evolve at a steady, stable rate 2) Punctuated Equilibrium = species arise abruptly and are quite different from the species they came from - seen in the fossil record where large gaps seem to appear from one to another

45. Rates of Speciation

49. Basic Definition of Evolution = Earth’s present day species developed from earlier, distinctly different species through the process of natural selection