1. Hemichordata and Invertebrate Chordates
Chapter 17 Notes

2. Relationship between phyla
Animals in phyla Hemichordata & Chordata
Have pharyngeal slits
A series of openings in the pharyngeal region between the digestive tract and the outside of the body
A dorsal tubular nerve cord
Associated with the development of complex systems for sensory perception, integration, and motor response

3. Phylum Hemichordata “Hemi” = half “Chorda” = cord Common Members:
Acorn Worms
Burrow
Marine
Pterobranchs
Collar has arms with many ciliated tentacles
Habitat:
Live in/on marine substrates
Food:
Sediment
Suspended Organic Matter

4. Hemichordata Reproduction: Nervous System Dioecious (Acorn worms)
Ciliated larve “tornaria”
Asexual (Pterobranchia)
Budding
Nervous System
Dorsal & ventral nerve tracts
No major ganglia
Unspecialized sensory structures

5. Phylum Hemichordata Characteristics Marine Soft Bodied & Worm-like
Deuterostomate – anus forms from blastopore
Body divided into 3 Regions
Proboscis
Collar
Trunk

6. Pterobranchs Castings on a seashore at low tide
Hemichordata
Characteristics
Ciliated Pharyngeal slits
Open circulatory system
Complete Digestive tract
Dorsal Nerve Cord
Epidermal Nervous system
Pterobranchs Castings on a seashore at low tide

7. Phylum Chordata Very large group Habitats:
Vertebrates – Have a back bone
have a bony vertebrae surrounding nerve cord
Invertebrates - Do not have a back bone
examples
Habitats:
Marine
Freshwater
Terrestrial
Aerial
Presence of an endostyle or thyroid gland
Complete digestive tract
Ventral, contractile blood vessel (heart)

8. Phylum Chordata
4 Characteristics Seen in all Chordates at some point of their life:
Notochord “back cord”
a dorsal rod, with a sheath of connective tissue
Pharyngeal Slits
allow water to pass from pharynx to outside/
filter feeding mechanism
Dorsal Tubular Nerve cord
Post-anal tail

9. Phylum: Chordata Invertebrate Chordates Do not have a bony vertebrae
Sub Phylum: Urochordata
Tunicates (sea squirts)
Sub Phylum: Cephalochordata
Lancelets

10. Tunicates “sea squirts”
Sessile
Planktonic filter feeders
Development involves a tadpole-like larva
Nervous system:
Confined to body wall
1 ganglion - on the wall of the pharynx
No complex sensory organs

11. Lancelets Small, tadpole-like filter feeders
Live In shallow marine waters
Notochord extends from head to tail

12. Invertebrates vs. Vertebrates