1. Systematics BIOL 1407

2. What is Systematics? Comparative study of biological diversity Intent: Determine evolutionary relationships Photo Credit of 1 st Tree of Life: Charles Darwin, 1837, courtesy of Wikimedia Commons

3. Cladistics Method used today by most biologists and paleontologists

4. Clades Groups based on shared ancestry Clade = Ancestor + All Descendants

5. Clade: Tetrapods Common ancestor: Organism with four legs Branch point circled in red Clade = Ancestor + All Descendants

6. Clade: Amniotes Common ancestor: Organism with amniotic egg

7. Classroom Assessment Clade: Reptiles Photo Credit: Drágo, 2008, Wikimedia Commons

8. Traditional Systematics Groups based on common characteristics  evolutionary relationships Crocodile Photo Credit: Marco Schmidt, 2007, Wikimedia Commons Tuatara Photo Credit: Michael Hamilton, 2006, Wikimedia Commons

9. Cladistics Descendants can have very different characteristics Green Tree Python Photo Credit: Keith Hooks @ Riverbanks Zoo, 2006, Wikimedia Commons Crimson Sunbird Photo Credit: Lip Kee Yap, 2008, Wikimedia Commons

10. Traditional Reptiles & Birds Traditional: Different-looking descendants placed in different groups Class Reptilia Class Aves ScalesFeathers No FlightFlight “Cold- blooded” “Warm- blooded”

11. Cladistics: Modern Reptiles Molecular data + new fossils  Birds and reptiles share common ancestor Clade Reptilia = Traditional Reptiles + Birds Photo Credit of Red Lory Preening: Andrew Kraker, 2008, Wikimedia Commons

12. Types of Groups Monophyletic Group = Clade Paraphyletic: Some descendants missing Polyphyletic: Do not share same recent common ancestor

13. Question? What kind of group is the traditional reptiles?

14. Convergent Evolution Similar selection pressures  Similar traits evolve Unrelated organisms look very similar Marsupial Mole Placental Mole

15. Classroom Assessment Photo Credit for Marsupial Mole: Magnus Manske, 2007, Wikimedia Commons Photo Credit for Star-Nosed Mole: Kenneth C. Catania, 2006, Wikimedia Commons

16. Cladograms Shows evolutionary history of a group Based on cladistics

17. A Cladogram Hypotheses about evolutionary relationships Based on available data May change with additional data

18. Cladogram Can be drawn differently Same tree as previous slide

19. Names of Clades Clade names = Labels next to branching points ≠ Names of the common ancestors

20. Terminal Taxa Located at ends of branches No descendants on tree Not always extant (living)

21. Sister Taxa More closely related to each other than to any other taxon Share a more recent common ancestor

22. Question? What is the sister taxon of the birds?

23. Question? What is the sister taxon of the Bird and Saurischian Dinosaur Clade?

24. Question? What is the sister taxon of the Dinosaur Clade?

25. Question? What is the sister taxon of lizards and snakes?

26. Question? What is the sister taxon of the mammoth, Mammuthus?

27. Question? What is the sister taxon of the African elephants?

28. Question? What is the sister taxon to the dinosaur clade?

29. Characters = Traits

30. Loss of Trait = Character

31. Types of Characters Shared primitive: Found in all Shared derived: Found in some but not all Unique derived: Found in only one

32. Shared Primitive Character

33. Shared Derived Character

34. Perspectives Shared primitive? Shared derived? Matter of perspective

35. Perspectives

36. Hinged Jaws: Shared Primitive? Shared Derived? Gnathostomes Vertebrates Chordates

37. Unique Derived Character Gnathostomes Vertebrates Chordates

38. Question? Which character is unique derived?

39. Question? Which character is shared primitive for tetrapods?

40. Question? Which character is shared derived for tetrapods?

41. Classroom Assessment: The Mars Mission Photo Credit: Marty Wise, 2004

42. The End Unless otherwise specified, all images in this presentation came from: Campbell, et al. 2008. Biology, 8 th ed. Pearson Benjamin Cummings.