Lecture 21 – Chordata A. Chordata Characteristics (4 classes: vertebrata refers to having a back bone, all other members of chordate; cephalochordate “head string” lancelets; urochordata “tail string” only have notochord in tail; ex: sea squirts”) 1. Coelomate 2. Bileral symmetry 3. Three germ layers - triploblastic 4. Tube-within-a-tube – every member has a complete digestive system 5. Segmented 6. Closed circulatory system – all members have this (decided this within the last 5 years) ONLY CHORDATES HAVE THESE (in order to be considered one you must posses all four of these during some point in your life cycle): 7. Tail posterior to anus (fig. 31-4) – at least at some point in their life cycle 8. Notochord – longitudinal rod, flexible and firm for support; we start out with this but our vertebral column replaces it 9. Dorsal, hollow, tubular nerve cord – unlike lower organisms who have solid, ventral, and two nerve cords 10. Pharyngeal gill slits – have this when we’re embryos
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This note was uploaded on 05/30/2008 for the course BS 131 taught by Professor Smith during the Spring '08 term at University of the Sciences in Philadelphia.