Evolutionary Patterns, Rates, and Trends

1. Evolutionary Patterns, Rates, and Trends Chapter 13

2. Asteroid Impacts • Many past catastrophic impacts altered the course of evolution • Iridium layer implicates asteroid in extinction of dinosaurs • Asteroids are still a threat

3. Macroevolution Large-scale patterns, trends, and rates of change among families and other more inclusive groups of species

4. Impacts, Issues Video Measuring Time

5. Fossils • Recognizable evidence of ancient life

6. What do Fossils Tell Us? • Each species is a mosaic of ancestral and novel traits • All species that ever evolved are related to one another by way of descent

7. Stratification • Fossils are found in sedimentary rock • This type of rock is formed in layers • In general, layers closest to the top were formed most recently

8. Sedimentary Rock

9. Radiometric Dating • Organism becomes buried in ash or sediments • Organic remains become infused with metal and mineral ions • Carbon 14 dating

10. Radiometric Dating parent isotope in newly formed rock after one half-life after two half-lives

11. Radioisotope decay Radiometric Dating

12. Radiometric dating

13. Geologic Time Scale Quaternary period Phanerozoic eon Cenozoic era Tertiary period • Boundaries based on transitions in fossil record 65 Mesozoic era Cretaceous period 145 Jurassic period 213 Triassic period 248 Paleozoic era Permian period 286 Carboniferous period 360 Devonian period 410 Silurian period 440 Ordovician period 505 Cambrian period Cambrian period 544 Proterozoic eon 2,500 mya Archean eon and earlier

14. Geologic time scale

15. Record Is Incomplete • Fossils have been found for about 250,000 species • Most species weren’t preserved • Record is biased toward the most accessible regions

16. Macroevolution • Major patterns and trends among lineages • Rates of change in geologic time

17. Continental Drift • Continents were once joined and have since “drifted” apart • Initially based on shapes • Later supported by world distribution of fossils and existing species, orientation of particles in iron-rich rocks

18. Plate Tectonics • Earth’s crust is fractured into plates

19. Geologic forces

20. Plate Tectonics • Movement of plates is driven by upwelling of molten rock at mid-oceanic ridges island arc oceanic crust oceanic ridge trench continental crust lithosphere (solid layer of mantle) hot spot athenosphere (plastic layer of mantle) subducting plate Fig. 13-6a, p.199

21. Plate margins

22. Comparative Morphology • Comparing body forms and structures of major lineages • Guiding principle: • When it comes to introducing change in morphology, evolution tends to follow the path of least resistance

23. Morphological Divergence 1 early reptile 2 3 4 5 1 2 3 pterosaur • Change from body form of a common ancestor • Produces homologous structures 4 1 chicken 2 3 1 2 bat 1 3 4 5 porpoise 2 4 5 3 penguin 2 3 1 2 human 3 4 5

24. Morphological divergence

25. Morphological Convergence • Individuals of different lineages evolve in similar ways under similar environmental pressures • Produces analogous structures that serve similar functions

26. Morphological Convergence

27. Comparative Development • Each animal or plant proceeds through a series of changes in form • Similarities in these stages may be clues to evolutionary relationships • Mutations that disrupt a key stage of development are selected against

28. Mutation and proportional changes Proportional Changes in Skull

29. Molecular Evidence • Biochemical traits shared by species show how closely they are related • Can compare DNA, RNA, or proteins

30. Biological Species Concept “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” Ernst Mayr

31. Genetic Divergence • Gradual accumulation of differences in the gene pools of populations • Natural selection, genetic drift, and mutation can contribute to divergence • Gene flow counters divergence

32. Reproductive Isolation • Cornerstone of the biological species concept • Speciation is the attainment of reproductive isolation • Reproductive isolation arises as a by-product of genetic change

33. Reproductive Isolating Mechanisms • Prevent pollination or mating • Block fertilization or embryonic development • Cause offspring to be weak or sterile

34. Reproductive Isolation Mechanisms

35. Reproductive isolating mechanisms Isolating Mechanisms

36. Prezygotic Isolation Mechanical isolation Temporal isolation Behavioral isolation Ecological isolation Gametic mortality

37. Mechanical Isolation • Wasp and zebra orchid

38. Temporal Isolation • Cicada

39. Temporal isolation among cicadas Reproductive Isolation

40. Behavioral Isolation • Albatrosses

41. Albatross courtship Reproductive Isolation

42. Postzygotic Mechanisms Early death Sterility Low survival rates

43. Models for Speciation • Allopatric speciation • Sympatric speciation • Parapatric speciation

44. Models of Speciation Models for Speciation

45. Allopatric Speciation • Speciation in geographically isolated populations • Some sort of barrier arises and prevents gene flow • Effectiveness of barrier varies with species

46. Allopatric Speciation

47. Extensive Divergence Prevents Inbreeding • Species separated by geographic barriers will diverge genetically • If divergence is great enough it will prevent inbreeding even if the barrier later disappears

48. Archipelagos • Island chains some distance from continents • Galapagos Islands • Hawaiian Islands • Colonization of islands followed by genetic divergence sets the stage for speciation

49. Allopatric speciation on an archipelago Models of Speciation

50. Hawaiian Islands • Volcanic origins, variety of habitats • Adaptive radiations: • Honeycreepers: in absence of other bird species, they radiated to fillnumerous niches