1. Invertebrate Chordates Copyright © McGraw-Hill Education Invertebrate Chordate Features Invertebrate chordates are deuterostomes with additional features that echinoderms lack. Include the lancelet (amphioxus) and tunicates

2. Invertebrate Chordates Copyright © McGraw-Hill Education Invertebrate Chordate Features Chordates have four distinctive features at some point in their development: A dorsal tubular nerve cord A notochord Pharyngeal pouches A postanal tail

3. Invertebrate Chordates Copyright © McGraw-Hill Education Invertebrate Chordate Features Chordates also have a coelom and segmentation Invertebrate chordates have a dorsal tubular nerve cord, a notochord, pharyngeal pouches, a postanal tail, and possibly an ancestral thyroid gland.

4. Invertebrate Chordates Copyright © McGraw-Hill Education Invertebrate Chordate Features Notochord The notochord is a flexible, rodlike structure that extends the length of the body. Allows the body to bend rather than shorten during muscle contractions

5. Invertebrate Chordates Copyright © McGraw-Hill Education Invertebrate Chordate Features Postanal tail A postanal tail is a structure used primarily for locomotion and is located behind the digestive system and anus. Tails in nonchordates contain a portion of the digestive tract.

6. Invertebrate Chordates Copyright © McGraw-Hill Education Invertebrate Chordate Features Dorsal tubular nerve cord The dorsal tubular nerve cord is located dorsal to the digestive organs and is a tube shape. The anterior end of this cord becomes the brain and the posterior end becomes the spinal cord during development of most chordates.

7. Invertebrate Chordates Copyright © McGraw-Hill Education Invertebrate Chordate Features Pharyngeal pouches Pharyngeal pouches connect the muscular tube that links the mouth cavity and the esophagus. Have slits for filter feeding and gills in aquatic chordates; in terrestrial chordates, developed into the tonsils and the thymus gland.

8. Invertebrate Chordates Copyright © McGraw-Hill Education Invertebrate Chordate Features Ancestral thyroid gland Thyroid gland regulates metabolism, growth, and development Invertebrate chordates have an endostyle, cells that secrete proteins similar to a thyroid.

9. Invertebrate Chordates Copyright © McGraw-Hill Education Diversity of Invertebrate Chordates All invertebrate chordates are marine animals. 23 species of lancelets 1250 species of tunicates

10. Invertebrate Chordates Copyright © McGraw-Hill Education Diversity of Invertebrate Chordates Lancelets Small, fishlike animals without scales Burrow their bodies into the sand in shallow seas Filter feeder

11. Invertebrate Chordates Copyright © McGraw-Hill Education Diversity of Invertebrate Chordates Lancelets Swim with a fishlike motion No heads or sensory structures other than light receptors and small sensory tentacles The nervous system consists of main branching nerves and a simple brain.

12. Invertebrate Chordates Copyright © McGraw-Hill Education Diversity of Invertebrate Chordates Tunicates Sessile Only in the larval stages do they show typical chordate features The only chordate feature that remains in the adult tunicate is pharyngeal gill slits and the thyroid gland.