ch 25: hemichordata & chordata Flashcards
what do chordate feats is hemichordata missing
- notochord
- post anal tail
4 hemichordates feats
- dorsal hollow nerve cord
- pharyngeal slits
- proboscis
- collar
pterobranchs feats (4)
- small colonial filter feeders/zooids
- resemble bryozoans
- live in tubes
- have unciliated tentacles on arms
graptolites
fossils of pterobranchs used to date Paleozoic rocks
enteropneusts
acorn worms
2 functs of acorn worm proboscis
- burrowing in soft mud
- eat mud/collect food
3 feats of enteropneusts
- no real brain or specialized sense organs
- open fert
- w is forced out pharyngeal slits
notochord
- formed from dorsal mesoderm
- forms discs btwn backbone
subphylum urochordata feats (2)
- most sedentary sea squirts
- a few are pelagic or planktonic
tunic =
outer coating strengthened by cellulose-like carb called tunicin
inside sea squirt tunic (3)
- modified pharynx
- endostyle secretes sheets of mucus
- branches of air syst
sea squirt nerve ganglion (2)
- controls squirting and cilial beating
- sensory cells detect toxins and sedi
can sea squirts be colonial
yes
sea squirt repro (2)
- asexual repro via budding
- sexually - hermaphrodites (open fert?)
sea squirt larvae (3)
- tadpole swims but does not feed
- seeks settling spot
- better sensory sys then adults
thaliaceans are often seen as
planktonic colonies prod by asexual budding
subphylum cephalochordata
lancelets
lancelets feats (5)
- retain chordate feats into adulthood
- filter feed using mucus sheets in pharynx
- endostyle secretes iodine-containing compound
- no real brain
- closed circ
conodonts
microscopic lancelet fossils used to date rocks
