The document discusses the characteristics of the phylum Chordata. It notes that all chordates possess a notochord, dorsal nerve cord, and gill slits at some point in their development. It describes two subphyla: Cephalochordata, which includes Amphioxus/lancelets, and Urochordata, which includes Tunicates/sea squirts. Tunicates are filter feeders that have a notochord and nerve cord as larvae but lose these traits as adults, while Amphioxus retains its notochord throughout life but never develops a backbone.

1. Phylum Chordata Subphylum Vertebrata Subphylum Cephalochordata Subphylum Urochordata have backbone fish birds reptiles amphibians mammals Amphioxus (or “lancelets”) Tunicates (or “sea squirts”)

2. Characteristics of Phylum Chordata At some point, all chordates have: gill slits muscular tail notochord (semi-rigid, rodlike structure) along the length of their body dorsal nerve cord (bundle of nerves that lies above the notochord)

3. adult tunicates (sea squirts)

4. Tunicates: filter feeders have organs sessile as adults motile larvae have a notochord and nerve cord notochord disappears in the adult

5. larval tunicate

6. larval tunicates in eggs

8. adult tunicate

9. Adult Tunicates (Sea Squirts)

10. NPR story about invasive tunicates in Puget Sound http://www.npr.org/templates/story/story.php?storyId=7602142

11. Amphioxus (or Lancelet)

12. Amphioxus: approx. 3 inches long filter feeders retains the notochord its entire life but never develops a backbone

14. Amphioxus (magnified)

15. Vertebrates: have notochord as embryos but eventually develop a backbone that surrounds the dorsal nerve cord all have gill slits and muscular tails as embryos; some are retained and some disappear during development 5 classes (birds, fish, reptiles, amphibians, mammals) with diverse characteristics