Invertebrate
Chordates
Hemichordata
Urochordata
Cephalochordata
Hemichordates
Deuterostomes
 Gill slits
 Dorsal nerve cord

Classes of Hemichordates

Enteropneusta
– Acorn worms
– Shallow marine animals

Pterobranchia
– Rhabdopleura
– Colonial, send out feeding zooids
Acorn Worm
Phylum Chordata
All chordates are deuterostomes
 At some time in their life, all chordates
have:

– Notochord
– Pharyngeal gill slits
– Dorsal, hollow nerve cord
– Postanal tail
Subphylum Urochordata
Sea squirts or tunicates
 Larvae show the characteristics of
chordates
 Adults lose notochord, nerve cord, and
tail
 Only animals to have cellulose in their
bodies!

Tunicates:
Are filter feeders
 Do not have complex nervous systems
 Often form large colonies
 Are monoecious

Tunicate Larva
Adult tunicates
Subphylum Cephalochordata
Lancelets (Amphioxus)
 Notochord runs from head through tail
 Muscles can contract the notochord
 Live partially buried in marine sediment
 Filter feeders
 Dioecious
