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Systematics

Systematics. BIOL 1407. 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. Cladistics.

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Systematics

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  1. Systematics BIOL 1407

  2. What is Systematics? • Comparative study of biological diversity • Intent: Determine evolutionary relationships • Photo Credit of 1st 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 AssessmentClade: 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

  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? Chordates Vertebrates Gnathostomes

  37. Unique Derived Character Chordates Vertebrates Gnathostomes

  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, 8th ed. Pearson Benjamin Cummings.

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