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Hemichordata and Invertebrate Chordates Chapter 17 Notes 1.

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1 Hemichordata and Invertebrate Chordates Chapter 17 Notes 1

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 2

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

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

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

6 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 6

7 Phylum Chordata Very large group – 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) 7

8 Phylum Chordata 4 Characteristics Seen in all Chordates at some point of their life: 1.Notochord “back cord” a.a dorsal rod, with a sheath of connective tissue 2.Pharyngeal Slits a.allow water to pass from pharynx to outside/ b.filter feeding mechanism 3.Dorsal Tubular Nerve cord 4.Post-anal tail 8

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

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 10

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

12 Invertebrates vs. Vertebrates 12

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