1. CHAPTER 5 Processes of Macroevolution

2. Chapter Outline  Discovering the Human Place in the Organic World  Principles of Classification  Constructing Classifications and Interpreting Evolutionary Relationships  Definition of Species  Interpreting Species and Other Groups in the Fossil Record  What Are Fossils and How Do They Form?

3. Chapter Outline  Vertebrate Evolutionary History: A Brief History  Mammalian Evolution  The Emergence of Major Mammalian Groups  Processes of Macroevolution  Working Together: Microevolution and Macroevolution

4. Focus Question  Where do humans fit in the story of life on the Earth?

5. The Human Place in the Organic World  To deal scientifically with the tremendous diversity of life on the planet, biologists develop a system of classification.

6. Classification  Organizes diversity into categories  Indicates evolutionary and genetic relationships  The kingdom Animalia includes 20 major phyla (singular, phylum)  Chordata is one phyla and includes all animals with a nerve cord, gill slits and supporting cord along the back.

8. Vertebrates  Animals with segmented, bony spinal columns; includes fishes, amphibians, reptiles, birds, and mammals.

9. Principles of Classification  The field that establishes the rules of classification is taxonomy.  Organisms are classified first on the basis of physical similarities.  Basic physical similarities must reflect evolutionary descent in order for them to be useful.

10. Principles of Classification  Homologies  Similarities based on a common ancestor.  Analogies  Similarities based on common function, with no assumed common evolutionary descent.  Homoplasy  Separate evolutionary development of similar characteristics in different groups of organisms.

11. Homologies  Similarities in the forelimb bones of these animals can be most easily explained by descent from a common ancestor.

12. Homologies vs. Analogies  How could an evolutionary biologist determine if a trait is an analogy or a biology?

13. Constructing Classifications and Interpreting Evolutionary Relationships  Evolutionary systematics  A traditional approach in which presumed ancestors and descendants are traced in time by analysis of homologous characters.  Cladistics  Attempts to make rigorous evolutionary interpretations based solely on analysis of certain types of homologous characters (those considered to be derived characters).

14. Clade  Lineage, or a group of organisms sharing a common ancestor.  The group includes the common ancestor and all descendants.

15. Ancestral and Derived (Modified) Characters  Ancestral  Characters inherited by a group of organisms from a remote ancestor and not diagnostic of groups that diverged after the character appeared; also called primitive.  Derived (Modified) Characters that are modified from the ancestral condition and thus are diagnostic of particular evolutionary lineages.

16. An Example of Cladistic Analysis: Evolution of Cars and Trucks  From a common ancestor of all passenger vehicles, the first major divergence is between cars and trucks (I).  A later divergence occurs between luxury cars and sports cars (II).  Derived features of each grouping appear after its divergence from other groups.

17. An Example of Cladistic Analysis: Evolution of Cars and Trucks  In this “tree,” SUVs diverge from trucks, but like sports cars, have a decorative racing stripe.  This is a homoplasy and does not make SUVs sports cars.  Classifications based on one characteristic that can appear in different groups can lead to an incorrect conclusion.

18. Using Cladistics to Interpret Real Organisms: Birds and Dinosaurs  Traditional view, no close relationship.

19. Using Cladistics to Interpret Real Organisms: Birds and Dinosaurs  Revised view, common ancestry of birds and dinosaurs.

20. Theropods  Small- to medium-sized ground-living carnivorous dinosaurs, dated to approximately 150 mya and thought to be related to birds.

21. Shared Derived  Relating to specific character traits shared in common between two life-forms and considered the most useful for making evolutionary interpretations.  The presence of feathers in the proposed relationship between some (theropod) dinosaurs and birds is an example

22. Phylogenetic Tree  A chart showing evolutionary relationships as determined by evolutionary systematics.  It contains a time component and implies ancestor descendant relationships.

23. Cladogram  A chart showing evolutionary relationships as determined by cladistic analysis.  It’s based solely on interpretation of shared derived characters.  It contains no time component and does not imply ancestor-descendant relationships.

24. Cladogram  This cladogram shows relationships of birds, dinosaurs, and other terrestrial vertebrates.  There’s no time scale and ancestor-descendant relationships aren’t indicated.

25. Cladograms vs. Phylogenetic Trees  How are these two approaches combined by physical anthropologists?

26. Definition of Species  The biological species concept emphasizes interbreeding and reproductive isolation

27. Speciation  Process by which a new species evolves from a prior species.  Speciation is the most basic process in macroevolution.

28. Speciation Model  A and B have not yet diverged.

29. Speciation Model  A and B are just beginning to diverge.  Genetic differences accumulate (mutation, genetic drift)  If different habitats, different selective pressures

30. Speciation Model  A and B have diverged to a point where they’re no longer able to reproduce; speciation is complete.

31. Speciation and the Processes of Evolution  Why is an understanding of the various processes of evolution important to understanding speciation?

32. Interpreting Species and Other Groups in the Fossil Record  The goal is to make meaningful biological statements about the variation represented in groups of organisms.  Identifying individual variation, age changes, variation due to sex (sexual dimorphism)  Fossil species are understood based on observations of living animals

33. Intraspecific variation  Variation accounted for by individual, age, and sex differences seen within every biological species

34. Interspecific variation  Variation representing differences between reproductively isolated groups

35. Recognition of Fossil Genera  A genus is a group of species composed of members more closely related to each other than to species from any other genus.  Species that are members of the same genus share the same broad adaptive zone.  Members of the same genus should all share derived characters not seen in members of other genera.

36. Fossils  Traces of ancient organisms and formed in several ways  Mineralization occurs very slowly as water carrying minerals, such as silica or iron, seeps into the tiny spaces within a bone. In some cases, the original minerals within the bone or tooth can be completely replaced.  Traces of life forms that include insects trapped in tree sap, leaf imprints, footprints, skeletal remains and remains of digestive tracts  Taphonomy is the study of how bones and other materials come to be buried in the earth and preserved as fossils

38. Geological Time Scale  The organization of earth history into eras, periods, and epochs; commonly used by geologists and paleoanthropologists.

39. Geological Time Scale

40. Geological Eras  Paleozoic  Vertebrates appeared 500 mya.  Mesozoic  Reptiles were dominant land vertebrate, placental mammals appeared 70 mya.  Cenozoic  Divided into Tertiary and Quaternary periods and 7 epochs.

41. Continental Drift  The movement of continents on sliding plates of the earth’s surface.  As a result, the positions of large landmasses have shifted drastically during the earth’s history.

42. Continental Drift  The positions of the continents during the Mesozoic (c. 125 mya.).  Pangea is breaking up into a northern landmass (Laurasia) and a southern landmass (Gondwanaland).

43. Continental Drift  The positions of the continents at the beginning of the Cenozoic (c. 65 mya).

44. Epochs  Categories of the geological time scale.  In the Cenozoic, epochs include  Paleocene  Eocene  Oligocene  Miocene  Pliocene  Pleistocene  Holocene

46. Mammalian Evolution  The Cenozoic era, the Age of Mammals.  The enlargement of the cerebrum, especially the neocortex, which controls higher brain functions, resulting in more nerve cells  A longer, more intense period of growth in utero  Distinctive dentition, termed a heterodont dentition, with 3 incisors, 1 canine, 4 premolars, and 3 molars in each quarter of mouth  Maintenance of constant internal body temperature, warm-bloodedness, and endothermic

47. Early Vertebrate Evolution

48. Lateral View of the Brain  Lateral view of the brain in fishes, reptiles, and primates.  Note the increased size of the cerebral cortex of the primate brain.

49. Reptilian and Mammalian Teeth  Reptilian teeth (top) are homodont.  Mammals are heterodont, they have different kinds of teeth; incisors, canines, premolars, and molars.

50. Endothermic  Able to maintain internal body temperature by producing energy through metabolic processes within cells; characteristic of mammals, birds, and perhaps some dinosaurs.

51. Emergence of the Major Mammalian Groups  Monotremes  Placental

52. Processes of Macroevolu tion  Operate on the whole species, rather than on individuals or populations  Take a longer period of time to have a noticeable impact

53. Adaptive Radiation  A process that takes place when a life form rapidly takes advantage of the many newly available ecological niches.  A species, or group of species, will diverge into as many variations as two factors allow: 1. Its adaptive potential. 2. The adaptive opportunities of the available niches.

54. Generalized and Specialized Characteristics  Refer to the adaptive potential of a particular trait  Generalized if a trait is adapted for many functions: a mammalian limb with five fairly flexible digits, adapted for many possible functions  Specialized if a trait is limited to a narrow set of functions: hand or foot suited for specialized function of stable weight support in an upright posture

55. Why It Matters Question  Why is it useful to know about the age of the earth and continental drift? What does this have to do with “us” and our world today? What does it really matter if the earth is only a few thousand years old, as some people claim?

56. Why It Matters We have reason to be concerned about the power of nature and one approach is to study geological beds that are millions of years old. From this record we can compute the periodicity of major earthquakes and volcanic eruptions.

57. QUICK QUIZ

58. 1. The scientific discipline that delineates the rules of classification is a) paleontology. b) stratigraphy. c) homology. d) taxonomy.

59. Answer: d  The scientific discipline that delineates the rules of classification is taxonomy.

60. 2. An advantage of heterodont dentition is that it a) allows the animal to defend itself more efficiently. b) allows for processing a wide variety of foods. c) opens up new ways of interacting with potential mates. d) allows the animal to grab prey that it could not catch otherwise.

61. Answer: b  An advantage of heterodont dentition is that it allows for processing a wide variety of foods.

62. 3. The uneven, nongradual evolutionary process of long stasis and quick spurts has been termed _________________. a) punctuated equilibrium b) gradualism

63. Answer: a a) Punctuated equilibrium refers to the uneven, nongradual process of long stasis and quick spurts.

64. 4. The divergence of reptiles into many different forms describes a) analogies. b) sexual selection. c) adaptive radiation. d) homologies.

65. Answer: c  The divergence of reptiles into many different forms describes adaptive radiation.

66. 5. Given the huge amount of organic diversity displayed in the record, as well as the vast amount of time involved, two major organizing perspectives prove indispensible. The perspectives are: a) schemes of formal classification b) geological time scale c) timeframe for next major earthquake d) a and b e) None of the above

67. Answer: d  Perspectives gained from schemes of formal classification and geological timescale prove indispensible for organizing understanding of organic diversity in the record.