1. Introduction to Chordates Chapter 15

3. Basics Bilateral symmetry Segmented body Three germ layers Well-developed Coelom Endoskeleton Complete digestive system Closed circulatory system

4. Chordate Characters 1.Notochord 2.Pharyngeal pouches 3.Postanal tail 4.Nerve cord (dorsal)

5. Notochord Flexible rod-like structure First part of endoskeleton (in embryo) Axis for muscle attachment In most verts, its replaced by vertebrae

6. Pharyngeal pouches Pharyngeal slits: vary in degree and function –Aquatic chordates: leads to outside of cavity –Amniotes: forms only groves –Fish: became gills

7. Postanal tail Tail and musculature provide motility –Fish: highly evolved –Other groups: become vestigial

8. Nerve cord Dorsal to alimentary canal Tubular Brain on anterior end Formed from ectoderm

9. SP: Urochordata Tunicates

10. SP: Urochordata Tunicates Found at all ocean depths –Largely sessile Larval forms have all chordate features –Adults loose many of these Notochord and tail disappear Dorsal nerve cord is reduced Tunic (test): protective covering around animal

11. Adult Tunicates

12. Adult and Tadpole Larva of Urochordate

13. SP: Urochordata Example Ascidians: sea squirts –More common intertidal animals –Can be found attached to rocks –Colonial and solitary forms Feeding –Filter feed with mucus net

15. SP: Cephalochordata Lancelets Marine Found in sediments near costal waters Feeding –Filter feed with mucus net

16. Lancelet Amphioxus

17. SP: Cephalochordata Bauplan Long slender, translucent Has four chordate characters Is though to be living descendant of ancestor that gave rise to vertebrates

18. SP: Vertebrata AKA Craniata: all groups have a cranium –braincase Thought to be monopyletic Share other important characteristics

19. SP: Vertebrata Fossil invertebrate chordates are rare and known primarily from two fossil beds. Pikaia from Cambrian Burgess Shale

20. Haidouella 530 MYO China

22. The Early Vertebrates Ostracoderms- Armed Jawless Fishes 505 MYO

23. SP: Vertebrata Living Endoskeleton Efficient Respiration (Pharynx) Advanced Nervous System Paired limbs

24. Living Endoskeleton Grows with body –No molting –Efficient use of materials Muscle attachment Protect body and body protects it Made from –Bone –Cartilage

25. Efficient Respiration (Pharynx) Pharynx is result of shift from filter feeding Increased metabolic rate –Addition of capillaries –Muscular aortic arches

26. Advanced Nervous System Predation favored more complex nervous system –Eyes with lenses –Paired eyes Two innovative adaptations –Neural crest-forms cranium –Specialized Sense Organs- nose, eyes, ears….

27. Paired limbs Pectoral and pelvic appendages –Swimming stabilizers Jointed limbs –Work well in terrestrial environments

28. The Big Picture Four major evolutionary events binds the chordates into a group –Many of these allowed chordates to be successful on land Urochordates as adults appear to be sponges or cnidarins, but as larvae they have all structures shared by chordate Remember what it means to be a vertebrate…