Chordate Lecture Flashcards
Chordata shared ancestral characteristics
bilateral symmetry, metamerism, coelom, anteroposterior axis, cephalization
Chordate Synapomorphies
notochord, single dorsal tubular nerve cord, pharyngeal slits/pouches, endostyle, postnatal tail
notochord is?
a flexible rod-like structure
notochord position?
ventral to nerve cord
notochord function?
locomotion –> skeletal axis for muscle attachment to facilitate undulatory movement
notochord appearance in the embryo?
as first part of the endoskeleton
notochord persists after embryo?
in protochordates (some) and jawless vertebrates
notochord replaced by?
cartilaginous or bony vertebrae in jawed vertebrates
nerve cord initially?
hollow tube but mostly fills in during development in most taxa
nerve cord produced by?
infolding of dorsal cells
anterior end of nerve cord?
in vertebrates, becomes brain
pharyngeal groove formation?
inpocketing of ectoderm
pharyngeal pouch formation?
outpocketing of adjacent endodermal lining of pharynx
pharyngeal slit formation?
fusion of inpockets and outpockets (aquatic chordates)
pharyngeal pouches produce?
middel ear cavity, Eustachian tube, other structures (amniotes)
pharynx & pharyngeal slits originally evolved as a?
filter feeding apparatus
in aquatic vertebrates, the pharynx is a?
respiratory organ (internal gills)
endostyle function? (protochordates & lamprey larvae)
for trapping food particle in the pharynx
endostyle function? (vertebrates & lamprey adults)
derives thyroid gland
endostyle evidence of homology?
endostyle & thyroid gland both secrete rare proteins w with iodine (rare in nature, t.f. homologous)
postanal tail function?
associated somatic musculature for propulsion in water (with great diversity of form and function across taxa)
“Urochordata”
“tunicates”
Urochordata notochord
restricted to tail in larva, and disappears during metamorphosis into adult
Urochordata ascidian larvae have?
tiny tadpoles with all 5 chordate synapomorphies (adults only retain pharyngeal slits & endostyle)
Urochordata ascidian larvae feed?
non-feeding, instead swim around and attach to solid object, metamorphoses into adult
Urochordata ascidian adult live?
most sessile (attached to substrate)
Urochordata ascidian adult feed?
filter feed with incurrent/excurrent siphons & endostyle
Urochordata ascidian adult reproduction?
hermaphroditic
“Cephalochordata”
“amphioxus” / “lancelets”
cephalochordata shape?
laterally compressed (elongate)
cephalochordata live?
in coastal waters w/ sandy bottoms
cephalochordata feed?
filter feed w/ cilia driven mechanisms
cephalochordata circulatory system?
closed
heart - blood pumped by contractions of aorta
cephalochordata blood + function?
colorless & no Hb or erythrocytes
+ transports nutrients but plays no role in gas exchange
cephalochordata nervous system? (3)
dorsal nerve cord retains tubular structure
unpaired nerve receptors on each side of the body
brain-life vesicle at anterior end of nerve cord
cephalochordata reproduction?
sexes separate
gametes releases our of atriopore
fertilization occures
ceohalochordata shares characteristics with
vertebrate body plan
- hepatic caecum (secretes enzymes to digest food)
- segmented trunk musculature
- basic plan of circulatory system
earliest known chordate?
(cephalochordata) “Pikaia”
found in Burgess Shale >500 myo
had notochord, myotomes, anteroposterior axis
phylogenetic relationship between chordate subphyla
old = U (CV) new = C (UV)
