7A Evidence of Common Ancestry

1. 7A Evidence of Common Ancestry

2. Summary of Darwin’s Theory Individuals with the VARIATIONS/ ADAPTATION best-suited to their environment will survive and reproduce. Those not suited will be less likely to breed (Survival of the fittest!)

3. Summary of Darwin’s Theory Species change over time, by passing on their useful (and harmful?) traits to their offspring

4. Summary of Darwin’s Theory THEREFORE, All species alive today have therefore descended with modificationsfrom ancient ancestors

5. Summary of Darwin’s Theory Ultimately, ALLorganisms on Earth are united into a single tree of life… Darwin’s original sketchbook drawing

8. This is…. Common Ancestry – the concept that a group of closely related species are all descended with some modifications from the same ancestor Descent with modification –idea that living species have descended with changes due to adaptations and natural selection from species that lived before them

9. Is There Any Evidence For This Theory?

10. Evidence of Evolution #1: Fossil Record • Fossils – preserved remains or traces of ancient organisms • evidence that the world was much older than once thought • Fossils show how organisms have changed over time Did you know??? 99% of species that once lived are now extinct!!!

11. The Geological Timescale Based on fossil evidence, it appears that the nature and diversity of life on our planet has changed dramatically throughout Earth’s history

12. Fossil Record When comparing fossils found in rock layers, the deeper the layer, the older the fossil.

13. Index Fossil – fossils of species that are easily recognizable, that lived during a specific geological time period, with a wide geographic range Are used to determine age of other fossils by comparing.

14. Evidence of Evolution #2: Biogeography Beaver Biogeography • The study of where species live now and where species and their ancestors lived in the past. • Shows common ancestry two ways: • Provide evidence as to how closely related species change in different environments/selection pressures • How distantly related groups have evolved similar traits under similar selection pressures Beaver Muskrat Beaver andMuskrat Coypu Capybara Coypu andCapybara Muskrat Capybara Coypu

15. Evidence of Common Ancestry #3: Homology • Homology is the study of similar characteristics between organisms • There are three major branches of homology: 1. Anatomical Homology 2. Embryological Homology 3. Molecular Homology

16. Anatomical Homology Homologous Structures -Same structure, different function - Same ancestor, different function On first appearance, would you say that a human hand, a bat’s wing and a whale’s flipper were the same structure?

17. Beneath The Surface… Homologous Structures –Same structure different function

18. Evidence of Evolution Analogous Structures: structures similar in function, but not inherited from a common ancestor. • Same function, different structure • different ancestor Flight Protection

19. Analogous structures have the same function but evolved from different places. -Analogous structures are also evidence for evolution because they show that two organisms that came from different ancestors, when placed under the same environmental pressures can evolve the same adaptations.

20. Vestigial Structures • Vestigial Structures • Structures that are inherited, but reduced in size and not used anymore Whale pelvic bone Human tailbone Human appendix

21. Embryological Homology • Embryology - the study of developing animals in its earliest stages • Embryos give evidence for evolution because many different kinds of organisms have embryos that look alike, suggesting that they all evolved from a common ancestor. The diagram below shows embryos of five different species: pig, chicken, fish, turtle, and human. Can you tell which is which?

22. Figured it out yet?

23. How about now?

24. Did you guess correctly?

25. Chicken – 2 ½ days Human – 31 days Pig – 21 days

26. Human – 9 weeks Lemur – 3 ½ weeks Pig – 30 days

27. Human face – 5 weeks

28. Human – 6 weeks Pig – 30 days Macaque monkey – 4 weeks

29. Limb Buds Pig foot – 30 days Human hand – 6 weeks Chicken foot – 5 days

31. Chimpanzee – 18 weeks Human – 16 weeks

32. Macaque monkey – 10 weeks

34. Human Embryo Development Time Lapse Animation: Click here for a time lapse animation. 4 weeks

35. Molecular Homology • All living things contain DNA and RNA. • Changes in Proteins, DNA and RNA can be traced from ancestors to their descendents. • The fewer differences there are between these molecules in different organisms, the more closely related they are CeleryProtein Apple Protein

36. DNA of Chimpanzee, Human, & Chicken Note – there are more differences between the human and chicken than the human and chimp With which organism do we share a more recent common ancestor?

37. Chromosome 1 of different species

38. Chromosome Homology Chromosome comparison of human, chimpanzee, gorilla, and orangutan

39. Human & Chimpanzee Chromosomes • Human on the left • Chimp on the right • Notice that Human Chromosome #2 appears to be a combination of Chimp Chromosomes #2 & 3

40. Checkpoint The table below demonstrates the amount of DNA overlap that five animals have with the DNA of a chimpanzee. Order the Animals From More Closely Related to Least Closely Related in their ancestral relationship with chimpanzees.