1. 1 Phylum Hemichordata Zoology- Mrs. Adams

2. “Half Chordate” Hemichordates display some characteristics of invertebrates and vertebrates Coelomates Deuterostomes Have dorsal and ventral nerve cord, gill slits, postanal tail, NO NOTOCHORD 2

3. Coelomates- true body cavity lined with mesoderm EX: all other animals

4. Protostomes vs. Deuterostomes Zygote cleaves to become blastula and then forms gastrula. The blastopore of the gastrula can become either the mouth or the anus of the organism Protostome- Blastopore becomes the mouth. Ex-Annelids, Mollusks and arthropods Deuterostome- Blastopore becomes anus. Ex- echinoderms, hemichordates,chordates

5. 5 Embryonic Development Protostome –Blastopore becomes mouth Deuterostome –Blastopore becomes anus

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7. 7 Phylum Hemichordata Three body regions –Proboscis –Collar –Trunk Deuterostome Gill slits Open circulatory system Dorsal and ventral nerve cord Ex. acorn worms

8. 8 Protostome=proboscis Collar trunk

9. Lifestyle 9 coastal and deep ocean benthic (live in sand) Rarely seen by humans Size ranges – a few millimeters to 1.5 meters Use proboscis to decompose organic material in sand Release feces(poop) in coils Separate sexes release gametes

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12. Checkpoint 12 1.What phylum includes animals that are considered to be “halfway” between invertebrates and vertebrates? 2.What are these animals called? 3.How are they different from other worm phyla we have studied? 4.Do they display all chordate characteristics? _____ Which ones do they display? 5.Where do these animals live? 6.What is their lifestyle? 7.Draw a sketch including the main three parts of their bodies.