1. Hemichordata and Invertebrate Chordates

2. Phylum Hemichordata All live marine environments.
Characteristics of Hemichordata:-
All live marine environments.
Bilaterally symmetrical.
Body divided into three sections, a proboscis, a collar and a trunk.

3. Body cavity a true coelom divided into three cavities.
Complete digestive tract, feeds on fine particles in the water.
Dorsal, sometimes tubular, nerve cord.

4. Class Enteropneusta Marine worms Ciliated epidermis and glands
cover acorn worms
Burrow in sandy and muddy substrates
Common name ‘acorn worms’

5. Maintenance Functions
Ventral Mouth
Lateral Pharyngeal slits,few to several hundred
Cilia and mucus assist acorn worms in feeding
Ciliary tracts converge near the mouth and form a mucoid string that enters the mouth

6. Eww!!! Enteropneusta extends its posterior end out of the burrow
during defecation.
Eww!!!

7. Nervous system Ectodermal in origin
Lies at the base of the ciliated epidermis
Consist of dorsal and ventral nerve tracts
No major ganglia
Sensory receptors are unspecialized

8. Respiration Simple diffusion of metabolic waste
Cilia associated with Pharyngeal slits circulate water into mouth and out of body
Gas exchange as water passes through pharyngeal slits

9. Circulatory system Colorless blood moves nutrients and wastes
Dorsal and ventral contractile vessel
Blood moves anteriorly in dorsal
Posteriorly in ventral vessel
Branches from theses vessels lead to open sinuses (Partially open circulatory system)
Anterior flowing blood moves through glomerulus (excretory organ)
Waste filtered into proboscis coelom and out through pores found in wall of proboscis

10. Reproduction and Development
Dioecious!!
pheromones
External Fertilization

11. Evolutionary ties b/w hemichordatres and echinoderms
Ciliated larvae

12. Class Pterobranchia pteron- wing branchia- gill Deep marine water
Some live in shallow waters

13. Body divided into three regions
Size mm

14. Individuals called zooids

15. Most live in secreted tubes in asexually produced colonies

16. Maintenance Functions
Filter feeders
Cilia on tentacles trap and transport
Food to mouth
Respiration and excretory exchange by diffusion

17. Reproduction and Development
Asexual budding is common and responsible for colony formation
Also some posses one or two gonads
Most species are dioecious
External fertilization
Planula-like larva (cnidarian)
Settles to a substrate, forms cocoon and metamorphoses into an adult

18. Phylum Chordata Characteristic of the chordates
Deuterostome embryo development Notochord, phayngeal slits or pouches, dorsal tubular nerve cord, and postanal tail
Coelomate animals
Bilateral symmetry
Endoskeleton
Two major groups: nonvertebrate chordates and vertebrates

20. Subphylum Urochordata
Uro, tail and chorda, cord
Class ascidians
Tunicates or sea squirts

21. Solitaire or colonial
Sessile adults
Attach to solid substrates
two siphons that permit seawater to circulate through the body
Oral siphon also the mouth
Atrial siphon

22. Body wall Tunic- gown Connective tissue like covering
Tough secreted by the epidermis
Composed of proteins
Salts, cellulose
Stolons extensions of tunic help root

23. Maintenance Functions
Longitudinal and circular muscles below the body wall epithelium
Nervous system largely confined to body wall
Forms nerve plexus with a single ganglion between oral and atrial opening
Sensitive to mechanical and chemical stimuli around siphon but no complex sensory organs

24. Reproduction and Development
Tadpole larva
Attaches to substrate by adhesive papillae located below the mouth
During development internal structures rotate 1800 bending the digestive tract into a U-shape

25. Reproduction and Development
Monoecious
Self fertilization and cross fertilization

26. Subphylum Cephalochordata
Elongated laterally flattened nearly transparent
Lancelets
Size up to 5 cm tadpole like animals
All four chordate characteristics persist throughout life
Shallow waters
genera Branchiostoma (Amphioxus)

27. Reproduction and Development
Dioecious
Gonads shed gametes into the atrium
Leave the body through the atriopore
External fertilization
Bilaterally symmetrical larva
Larva free swimming
Larva Settle to substrate then metamorph into adults

28. Maintenance Function Filter feeders Buried in sandy substrate
Mouth pointed upward

29. Edible particles move along cilia to the gut
Cilia on lateral surfaces of gill sweep water into mouth
Food sorted in the cirri
Edible particles move along cilia to the gut

30. No true heart
Contractile waves in the walls of major vessels propel blood
Blood contains amoeboid cells and bathes tissues in open spaces

31. Excretory tubules are modified coelomic cells closely associated with blood vessels.
Coelom reduced- restricted to canals near the gill bars, endostyle and the gonads