Origin & Evolution of Vertebrates Ch. 34

1. Origin & Evolution of VertebratesCh. 34 Lecture Objectives 1. Intro to Phylum Chordata

2. Echinodermata Cephalochordata ANCESTRAL DEUTEROSTOME Urochordata Notochord Myxini Common ancestor of chordates Petromyzontida Chondrichthyes Vertebrae Jaws, mineralized skeleton

3. Phylum Chordata 1. Bilateral 2. Segmented Body 3. Triploblastic 4. Coelomate 5. Deuterostomes

4. Chordate Hallmarks* May only appear during embryonic development. Dorsal, hollow nerve cord Muscle segments Notochord Mouth Anus Pharyngeal slits or clefts Muscular, post-anal tail Fig. 34.3

5. Chordate hallmarks con’t: Notochord Notochord

6. Chordate hallmarks con’t: Dorsal Hollow Nerve Cord

7. Chordate hallmarks con’t: Pharyngeal Slits

8. Chordate hallmarks con’t. Post-anal tail

9. Broken into 3 subphyla: Cepahlochordata (lancelets) Urochordata (tunicates) Vertebrata (animals w/backbones) Class Agnatha Class Amphibia Class Reptilia Class Aves Class Mammalia Phylum Chordata

10. Fig. 34-4 Subphylum: Cephalochordata (lancelets) Cirri Mouth Pharyngeal slits Atrium Notochord Digestive tract Atriopore Dorsal, hollow nerve cord Segmental muscles Anus Tail Fig. 34.4

11. Subphylum: Urochordata (tunicates) Fig. 34.5

12. 1. Chordates w/ a head 2. Higher metabolism 3. Increased muscle 4. 2 chambered heart 5. RBCs w/ hemoglobin 6. Pharyngeal slits  gills Subphylum Vertebrata: the craniates Segmented muscles Pharyngeal slits Fig. 34.9

13. Extant craniates: SP: Vertebrata, Class Myxini 1.Cyclostomes - Jawless, Ex. Hagfish 2. Cartilaginous skull & skeleton 3. Long & slender, eel-like 4. Bottom scavengers that secrete slime 5. Ingest food by sucking

14. Fig. 34-9 Slime glands Fig. 34.7

15. Extant craniates: SP: Vertebrata, Class Pteromyzontida 1. Cyclostomes, Ex. Lamprey 2. Marine & freshwater 3. Mostly ectoparasites 4. Skeleton made of cartilage

16. Fig. 34.8

17. Gnathostomes (jaw mouth) Ex. Sharks, Fish, Amphigians, Reptiles, Birds, Mammals 1. Jaws that may have evolved from skeletal supports of the pharyngeal slits 2. An enlarged forebrain associated with enhanced smell and vision 3. lateral line system Fig. 34.12

18. Tetrapods – gnathostomes with limbs • Four limbs, and feet with digits (from fins 365 mya) • Ears for detecting airborne sounds Fig. 34.19

19. SP: Vertebrata, Class Amphibia 1. Gnathostomes & Tetrapods w/ moist skin  complements the lungs in gas exchange 2. Fertilization is external in most species 3. Eggs require a moist environment Figs. 34.22-34.23

20. Amniotes: reptiles, birds, mammals 1. Tetrapods w/ terrestrially adapted egg 2. Relatively impermeable skin 3. Ability to use the rib cage to ventilate the lungs Fig. 34.25

21. SP: Vertebrata, Class Reptilia 1. Scales that create a waterproof barrier 2. Lay shelled eggs on land (or live birth) 3. Ectothermic or endothermic 4. Ex. lizards, snakes, turtles, crocodilians, and the extinct dinosaurs

22. Fig. 34.28

23. SP: Vertebrata, Class Aves 1. Wings with keratin feathers 2. Lack of urinary bladder 3. Reduction in reproductive organs 4. Loss of teeth

24. Finger 1 (b) Bone structure Palm (a) Wing Finger 2 Finger 3 Forearm Wrist Shaft Shaft Barb Vane Barbule Hook (c) Feather structure Fig. 34.29

25. SP: Vertebrata,Class Mammalia 1. Mammary Glands 2. Hair 3. Larger Brains 4. Differentiated Teeth

26. Variations in Class Mammalia 1. Embryo develops within a placenta in the mother’s uterus 2. Embryonic development completed while nursing in a maternal pouch • Marsupials 3. Egg laying mammals • Monotremes

27. Marsupials & Monotremes Figs. 34.37-34.38