Hemichordata and Invertebrate Chordates Chapter 17 Notes

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

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

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

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

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

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)

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

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

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

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

Invertebrates vs. Vertebrates