Chapter 16.3 and 16.4

1. Chapter 16.3 and 16.4 16.3 Darwin Presents His Case 16.4 Evidence for Evolution

2. 16.3: Evolution by Natural Selection • Under what conditions does Natural Selection occur?

3. Evolution by Natural Selection • The Struggle for Existence • More organisms are produced than can actually survive. • Leads to competition within the species

4. Evolution by Natural Selection • Variation and Adaptation • Any heritable characteristic that increases an organism’s ability to survive and reproduce in its environment is called an adaptation. • Those best adapted to the environment with survive more often and reproduce. • Their offspring will then have those same traits. • Species will eventually acquire those traits in general.

5. Evolution by Natural Selection • Survival of the Fittest • Fitness: • how well an organism can survive and reproduce in its environment. • The most well adapted organisms in the environment are “most fit”.

6. Evolution by Natural Selection • Natural Selection • Under what conditions does Natural Selection occur? • similar to Artificial Selection, but nature itself is imposing the force, selecting for or against certain traits as being favorable. • occurs in any situation in which more individuals are born than can survive… • Struggle for Existence • there is natural heritable variation… • Variation and Adaptation • there is variable fitness among individuals • Survival of the Fittest

7. Common Descent • What does Darwin’s mechanism for evolution suggest about living and extinct species?

8. Common Descent • Successful species can evolve into new species. • Descent with Modification • living species are descended, with modification, from common ancestors. • Deep Time gave enough time for natural selection to act.

9. Common Descent • What does Darwin’s mechanism for evolution suggest about living and extinct species? • According to the Principle of Common Descent, all species –living and extinct- are descended from ancient common ancestors. • A single “tree of life,” then, links all living things.

10. Common Descent • Tree of Life with Common Ancestry

11. 16.4: Evidence of Evolution • How does the distribution of species support evolution?

12. 16.4: Evidence of Evolution • Biogeography • How does the distribution of species support evolution? • Patterns in the distribution of living and fossil species tell us how modern organisms evolved from their ancestors.

13. 16.4: Evidence of Evolution • Biogeography • study of where organisms live now and where they and their ancestors lived in the past. • Two distinct pattern • 1. Closely related species differentiate in slightly different climates. • Ex: Finches and Tortoises on the Galapagos Islands • 2. Very distantly related species develop similarities in similar environments. • Ex: Flightless birds of South America, Africa and Australia

14. 16.4: Evidence of Evolution • The Age of Earth and Fossils • How do fossils support evolution?

15. 16.4: Evidence of Evolution • The Age of Earth and Fossils • How do fossils support evolution? • Many recently discovered fossils form series that trace the evolution of modern species from extinct ancestors. • Ex: Fig 16-13 • Evolution of whales from ancient land mammals. • Others include: • connections between dinosaurs and birds as well as fish and four-legged land animals.

16. 16.4: Evidence of Evolution • Comparing Anatomy and Embryology • How do homologous structures and embryology support evolution?

17. 16.4: Evidence of Evolution • Comparing Anatomy and Embryology • How do homologous structures and embryology support evolution? • According to evolutionary theory, organisms that share homologous structures have descended, with modification, from a common ancestor.

18. 16.4: Evidence of Evolution • Homologous Structures • Structures that are shared by related species and that have been inherited from a common ancestor. • Ex: • Fig 16-14 • Homologous Limb Bones

19. 16.4: Evidence of Evolution • Front limbs of reptiles and birds are more similar to each other then either is to the front limbs of an amphibian or mammal. • Reptiles and birds have a more recent common ancestor

20. 16.4: Evidence of Evolution • Note: *Analogous Structures • Bat wing and Fly wing • same function, different structure • unrelated • Analogous Structure • Bat wing and Horse leg • different function, similar (bone) structure • related • Homologous Structure • Common descent is common structure, not common function.

21. 16.4: Evidence of Evolution • Vestigial Structures • Physical structures present, but not used or selected for/against • typically just a trace or vestige of what it once was • Ex: hipbones of whales and dolphins • remnants of pelvic bones in dolphins’ ancestors

22. 16.4: Evidence of Evolution • Embryology • Similar patterns of embryological development provide further evidence that organisms have descended from a common ancestor.

23. 16.4: Evidence of Evolution • Genetics and Molecular Biology • What evidence of evolution comes from molecular biology?

24. 16.4: Evidence of Evolution • Genetics and Molecular Biology • What evidence of evolution comes from molecular biology? • The universal genetic code and homologous molecules provide evidence of common descent.

25. 16.4: Evidence of Evolution • Life’s Common Genetic Code • Different species that are closely related • more similarities in DNA • Different species that are distantly related • less similarities in DNA • Fig 16-16

26. 16.4: Evidence of Evolution • Testing Natural Selection • What does recent research on the Galapagos finches show about natural selection?

27. 16.4: Evidence of Evolution • Testing Natural Selection • What does recent research on the Galapagos finches show about natural selection? • Natural selection takes place in wild finch populations frequently, and sometimes rapidly. • Variation within a species increases the likelihood of the species’ adapting to and surviving environmental change.

28. Chapter 16.3-16.4 Assessment • What happens in the process of natural selection?

29. Chapter 16.3-16.4 Assessment • Why do organisms with greater fitness generally leave more offspring than organisms that are less fit?

30. Chapter 16.3-16.4 Assessment • How are natural selection and artificial selection similar? Different?

31. Chapter 16.3-16.4 Assessment • Why were Hutton’s and Lyell’s ideas important to Darwin?

32. Chapter 16.3-16.4 Assessment • What do evolutionary trees show?

33. Chapter 16.3-16.4 Assessment • What does a tree of life imply about all species living and extinct?

34. Chapter 16.3-16.4 Assessment • What is Biogeography

35. Chapter 16.3-16.4 Assessment • Why do species in very different places sometimes share similar structures?

36. Chapter 16.3-16.4 Assessment • Whay are fossils important evident for evolution?

37. Chapter 16.3-16.4 Assessment • How do vestigial structures provide evidence for evolution?

38. Chapter 16.3-16.4 Assessment • Explain the differences between homologous and analogous structures. Which are more important to evolutionary biologists? Why?