1. Macroevolution

2. Macroevolution The origin of taxonomic groups higher than the species level Concerned with major events in the history of life as found in the fossil record Includes the origin of new design features such as feathers and wings in birds, upright posture of humans Examines large scale evolutionary changes

3. Macroevolution major questions of macroevolution How do major novel features arise? What accounts for apparently progressive trends found in the fossil record? How has macroevolution been affected by global geological changes? What explains the major fluctuations in biological diversity seen in the fossil record?

4. Macroevolution movie

5. Fossil of a fish: perch Fossil of a fish: perch

6. Fossils Sedimentary rocks are the richest source –Formed from deposits of sand (compressed into sandstone) or silt (compressed into shale) Usually form from mineral rich hard parts of organisms Petrification – minerals dissolved in the groundwater seep into the tissues of the dead organism and replace organic matter Occasionally fossils retain organic matter (DNA)

7. Fossils come in variety of forms

8. Dinosaur National Monument –dinosaur bone in sandstone

9. Skulls of Australopithecus and Homo erectus

10. Petrified trees

11. Leaf impression Leaf impression

12. Dinosaur tracks (trace fossils)

13. Scorpion in amber

14. Mammoth tusks 23,000 years old (Siberia 1999)

16. Barosaurus

17. Limitations of the Fossil Record A fossil represents a sequence of improbable events A large fraction of species that have lived probably left no fossils Most fossils that were formed have probably been destroyed Only a fraction of the existing fossils have been discovered So… the fossil record is comprised primarily of species that lived a long time, were abundant and widespread, and had shells or hard skeletons

18. Early Earth Video

19. The Geologic Time Scale

20. Geological time scale movie 25T-01-GeologicTimeScale.mov

21. Dating Relative Dating Absolute Dating Radiometric dating (error of less than 10%) Half-life = Number of years it takes for 50% of the original sample to decay Carbon-14 (half-life = 5600 years) Best for dating material less than 50,000 yrs old Uranium-238 (half- life 4.5 billion years)

22. Evolutionary novelties (1) how do new designs evolve? Higher taxonomic groups such as families and classes are defined by evolutionary novelties (such as wings in birds) Mechanism is a gradual refinement of existing structures for new functions Structures may have an evolutionary plasticity that makes alternative functions possible

23. Evolutionary novelties (2) how do new designs evolve? Preadaptation –When a structure evolved in one context and becomes co-opted for another function –Natural selection can not anticipate the future, but can improve on an existing structure –Example: feathers in birds

24. Evolutionary novelties (3) how do new designs evolve? Genes that control development play a major role –A slight alteration in development becomes compounded in its effect on the adult –Allometric growth Differences in relative rates of growth of various body parts. A slight change in these realtive growth rates may yield a substantial change in the adult

25. Allometric growth

26. Genes controlling development Regulatory genes can effect hundreds of structural genes, so changes here have a great impact Paedomorphosis = Retention of features in the adult that were juvenile in ancestral species.

27. Paedomorphosis movie 24-21-PaedomorphosisAnim.mov

28. Paedomorphosis in axolotl (a salamander which retains some larval (tadpole) characteristics)

29. Genes controlling development Heterochrony = evolutionary changes in the timing or rate of development.

30. Heterochrony and the evolution of salamander feet among closely related species Feet are shorter with more webbing, better for climbing up a vertical surface. Possible influence of an evolutionary change in a regulatory gene which switches off foot growth earlier in tree-dwelling species

31. Genes controlling development Homeosis = alteration in the placement of different body parts

32. Evolutionary trends (1) At times it appears that there are trends in the fossil record (toward greater size, more feathers, etc.) A trend does not mean macroevolution is goal-oriented No intrinsic drive toward a preordained state of being is indicated by the presence of an evolutionary trend

33. Evolutionary trends (2) Species Selection –Species that exist the longest and generate the greatest number of new species determine the direction of major evolutionary trends –Differential speciation may play a role in macroevolution similar to the role of differential reproduction (natural selection) in microevolution

34. Evolutionary trends (3) A trend may cease or reverse itself under changing environmental conditions. –Conditions in the Mesozoic era favored giant reptiles, but by the end of that era the smaller species prevailed

35. The branched evolution of horses Hyracotherium to modern horses. Smooth progressive trend toward increased size, less toes and grazing teeth??? Not a straight line. It is just that Equus is the only survivor of a much more complicated evolutionary tree.

36. Biogeography and Continental Drift

37. Earth’s crustal plates and plate tectonics (geologic processes resulting from plate movements)

38. Crustal plate boundaries

39. San Andreas fault

40. History of continental drift PANGEA Ghana and Brazil are separated by 3000 km of ocean, but matching fossils in both areas show the areas were once connected.

41. Mass Extinctions and Adaptive Radiations Mass extinctions were followed by extensive diversification of some of the taxonomic groups that survived extinction. Surviving species are able to undergo new adaptive radiations into the vacated habitats and produce new diversity

42. Adaptive radiations Examples –Flying Insects –Mammals

43. Mass Extinctions Why? Habitat destruction? Unfavorable environmental conditions? Permian Extinctions –About 250 million years ago –90% of species were eliminated Cretaceous Extinctions –About 65 million years ago –Over 50% of species eliminated

44. Diversity of life and periods of mass extinction Diversity of life and periods of mass extinction

45. Trauma for planet Earth and its Cretaceous life The Asteroid Impact Hypothesis Immediate effect-Cloud of hot vapor and debris that could have killed most plants and animals in N. America in minutes?

46. Mass Extinction Video Mass Extinction Video Mass Extinction Video

47. The Sixth Extinction The Earth may be on the brink of a sixth mass extinction on a par with the five previous episodes This time it appears that the cause is the activities of a growing human population. Rate of species extinction estimated from the fossil record is about 10-100 per year. In tropical habitats alone the current rate may be 27,000 per year.

48. Systematics Phylogeny = the evolutionary history of a species or group Systematics = the study of biological diversity in an evolutionary context. –Taxonomy = identification and classification of species

49. Hierarchical classification

50. Homology/Analogy Homology –Likeness attributed to a shared ancestry –Forelimbs of mammals are homologous structures Analogy –Similarities due to convergent evolution, not common ancestry –Insect wings and bird wings are analogous structures

51. Homologous structures: anatomical signs of descent with modification Homologous structures: anatomical signs of descent with modification

52. Convergent evolution Acquisition of similar characteristics in species from different evolutionary branches due to sharing similar ecological roles with natural selection shaping analogous structures.

53. Convergent evolution and analogous structures Convergent evolution and analogous structures Ocotillo of SW North America Allauidia of Madagascar

54. Convergent evolution (bird beaks)

55. Systematics connects classification and phylogeny

56. Molecular Biology tools for systematics Protein comparison DNA sequence comparison These can be used to access relationships even between species so distantly related that no morphological similarities exist.

57. Phylogenetic Tree Cladogram –A dichotomous tree that branches repeatedly –Classifies organisms according to the order in time that branches arise. –Each branch point is defined by novel homologies unique to the various species on that branch

58. Cladograms

59. Constructing a cladogram

60. Cladistics and taxonomy Cladistics and taxonomy

61. Molecular clocks Based on the observation that some regions of genomes evolve at constant rates. By comparing DNA sequences from these regions or the proteins that result, an estimate of the time since the groups diverged can be estimated.

62. Dating the origin of HIV-1 M with a molecular clock Using a molecular clock method, a date for the origin of HIV infections in humans can be inferred. HIV seems to have descended from related viruses that infect chimpanzees and sooty mangabeys. When did the virus make the jump to the human species?? Projecting backward, the 1930s are the probable time of first human invasion by HIV.

63. Modern systematics is shaking some phylogenetic trees Traditionally, lizards, snakes, and crocs are classified together in the Class Reptilia with birds in a separate class (Aves) But crocodiles may actually be more closely related to birds than to lizards and snakes

64. Evolution of birds Archaeopteryx

65. Often you may hear critics of evolution theory claim that it is "just a theory," and that even scientists disagree about many of the details of the Earth's past and the origin of life. However, even though scientists do have heated discussions on the details, they do not disagree about the general claim of natural selection. As an example, currently there is a vigorous debate on exactly how and when birds evolved from dinosaurs. Although there is not agreement on every detail -- science is an on-going critical activity -- the evidence is solid that birds are the living descendants of theropod dinosaurs, birds are not the sole feather-bearing creatures, and feather- like structures preceded flight and hence did not evolve in connection with it. Darwin's theory predicts that a very important survival trait may initially evolve for a completely different reason than that for which it becomes a key survival trait. Feathers may have evolved in some dinosaurs for the purpose of communicating with potential mates and enemies or for moderating body temperature. Excerpt from Natural History Magazine.

66. Evolution of birds

67. http://www.npr.org/templates/story/story.php?storyId=931047 4-winged dinosaur Possible Feather evolution