Vertebrate Evolution and Diversity

1. Vertebrate Evolution and Diversity Chapter 34

2. The Vertebrate Clade

3. There are 4 features that distinguish chordates from other phyla… • Appearance of a notochord • Dorsal, hollow nerve cord • Pharyngeal slits • Post anal tail

4. What is a vertebrate anyway? • Has a neural crest • High degree of cephalization • Cranium • Most have a vertebral column • endoskeleton

5. 3 Subphyla PHYLUM CHORDATA Urochorodata Cephalochordata Vertebra Exhibit Paedogenesis Lancelets Trunicates (sea squirts) Larva shows some features of chordates Adults do not. Adults show all features

6. Paedogenesis may have occurred in vertebrate evolution. • Paedogenesis  Adult retains features seen in embryonic development because the larva display sexual maturity. Vertebrate Ancient Cephalochordate Adult Urochordate Paedogenesis No Paedogenesis Ancient Urochordate larva

8. Jawless vertebrates • Agnathans (hagfishes) • Lampreys (1st vertebral columns)

9. Fishes (Chodrichthyes and Osteichthyes) • The first vertebrates to have JAWS, evolved from pharyngeal slits, new features evolve from modifications of existing features.

10. Bearing young • Oviparous Lay eggs that hatch outside of mother, nourishment comes from egg yolk Mermaids purse • Ovoviviparous  Hatches within the uterus, nourishment comes from egg yolk. • Viviparous  Young develop inside the mother with nourishment from the placenta

11. Trend of cartilage to bone in embryonic development. • Sharks are cartilaginous fish  Class Chondrichthyes • So sharks evolved from ancestors that has bony skeletons (derived character not a shared character). • Allows them to swim very fast and be agile

12. Bony Fishes Osteichthyes • All have an endoskeleton • Have scales • Glands in skin secrete a mucus • Have a swim bladder

13. The need for legs Tetrapods

14. Making the transition to land, Arthropods have already done it, why can’t we? • Need an internal support • Need to conserve water • Need to reproduce near water or find some other way around losing water (self contained pond Amniotic egg) • Need to evolve limbs  tetrapods • Must keep own temperature  endothermic.

15. Acanthostega: An early tetrapod fish.

16. Class Amphibia: Dependence upon water. Means “Two lives” Respiration? Fertilization? Skin and crude lungs No diaphragm External fertilization And hatching near water

17. Reptiles are “cold blooded”Ectothermic • Warm blooded  endothermic • Why the need for endothermic on land?

18. The advent of the Amniotic egg: A self contained pond: Reptiles, lizards, snakes, turtles

19. The Evolution of flight  Class Aves: The birds

20. The evolution of flight  Birds Class Aves

22. Class Mammalia • Have mammary glands that produce milk. • The presence of hair (not fur, careful) • Endothermic high metabolism (efficient circulation 4 chambered heart • Born rather than hatched, fertilization in internal. • Placental (eutherian) animals nutrients diffuse through the placenta to fetus. • Evolved from reptiles.

23. Marsupials are special mammals • Born early in development and completes development externally in a pouch. • Nursing occurs in the pouch • Convergent evolution is the reason why some marsupials resemble placental counterparts. • Most in Australia

24. Placental (eutherian) Animals • Longer pregnancy • Young complete development in uterus, joined by the placenta

25. What is this then?

28. Mermaids’ Purse • Actually a skates egg.

29. Notochord • Longitudinal, flexible rod. • Fairly stiff, support.

30. Hollow Nerve Cord • Nerve bundles, dorsally located • Develops into the Central Nervous System

31. Pharyngeal Slits • Near pharynx, allow water to exit without going through the digestive tract. • Modified for gas exchange

32. Post anal tail • Muscular. • Propulsion