Chordate Lecture

Question 1

Chordata shared ancestral characteristics

Answer 1

bilateral symmetry, metamerism, coelom, anteroposterior axis, cephalization

Question 2

Chordate Synapomorphies

Answer 2

notochord, single dorsal tubular nerve cord, pharyngeal slits/pouches, endostyle, postnatal tail

Question 3

notochord is?

Answer 3

a flexible rod-like structure

Question 4

notochord position?

Answer 4

ventral to nerve cord

Question 5

notochord function?

Answer 5

locomotion –> skeletal axis for muscle attachment to facilitate undulatory movement

Question 6

notochord appearance in the embryo?

Answer 6

as first part of the endoskeleton

Question 7

notochord persists after embryo?

Answer 7

in protochordates (some) and jawless vertebrates

Question 8

notochord replaced by?

Answer 8

cartilaginous or bony vertebrae in jawed vertebrates

Question 9

nerve cord initially?

Answer 9

hollow tube but mostly fills in during development in most taxa

Question 10

nerve cord produced by?

Answer 10

infolding of dorsal cells

Question 11

anterior end of nerve cord?

Answer 11

in vertebrates, becomes brain

Question 12

pharyngeal groove formation?

Answer 12

inpocketing of ectoderm

Question 13

pharyngeal pouch formation?

Answer 13

outpocketing of adjacent endodermal lining of pharynx

Question 14

pharyngeal slit formation?

Answer 14

fusion of inpockets and outpockets (aquatic chordates)

Question 15

pharyngeal pouches produce?

Answer 15

middel ear cavity, Eustachian tube, other structures (amniotes)

Question 16

pharynx & pharyngeal slits originally evolved as a?

Answer 16

filter feeding apparatus

Question 17

in aquatic vertebrates, the pharynx is a?

Answer 17

respiratory organ (internal gills)

Question 18

endostyle function? (protochordates & lamprey larvae)

Answer 18

for trapping food particle in the pharynx

Question 19

endostyle function? (vertebrates & lamprey adults)

Answer 19

derives thyroid gland

Question 20

endostyle evidence of homology?

Answer 20

endostyle & thyroid gland both secrete rare proteins w with iodine (rare in nature, t.f. homologous)

Question 21

postanal tail function?

Answer 21

associated somatic musculature for propulsion in water (with great diversity of form and function across taxa)

Question 22

“Urochordata”

Answer 22

“tunicates”

Question 23

Urochordata notochord

Answer 23

restricted to tail in larva, and disappears during metamorphosis into adult

Question 24

Urochordata ascidian larvae have?

Answer 24

tiny tadpoles with all 5 chordate synapomorphies (adults only retain pharyngeal slits & endostyle)

Question 25

Urochordata ascidian larvae feed?

Answer 25

non-feeding, instead swim around and attach to solid object, metamorphoses into adult

Question 26

Urochordata ascidian adult live?

Answer 26

most sessile (attached to substrate)

Question 27

Urochordata ascidian adult feed?

Answer 27

filter feed with incurrent/excurrent siphons & endostyle

Question 28

Urochordata ascidian adult reproduction?

Answer 28

hermaphroditic

Question 29

“Cephalochordata”

Answer 29

“amphioxus” / “lancelets”

Question 30

cephalochordata shape?

Answer 30

laterally compressed (elongate)

Question 31

cephalochordata live?

Answer 31

in coastal waters w/ sandy bottoms

Question 32

cephalochordata feed?

Answer 32

filter feed w/ cilia driven mechanisms

Question 33

cephalochordata circulatory system?

Answer 33

closed

heart - blood pumped by contractions of aorta

Question 34

cephalochordata blood + function?

Answer 34

colorless & no Hb or erythrocytes

+ transports nutrients but plays no role in gas exchange

Question 35

cephalochordata nervous system? (3)

Answer 35

dorsal nerve cord retains tubular structure
unpaired nerve receptors on each side of the body
brain-life vesicle at anterior end of nerve cord

Question 36

cephalochordata reproduction?

Answer 36

sexes separate
gametes releases our of atriopore
fertilization occures

Question 37

ceohalochordata shares characteristics with

Answer 37

vertebrate body plan

• hepatic caecum (secretes enzymes to digest food)
• segmented trunk musculature
• basic plan of circulatory system

Question 38

earliest known chordate?

Answer 38

(cephalochordata) “Pikaia”
found in Burgess Shale >500 myo
had notochord, myotomes, anteroposterior axis

Question 39

phylogenetic relationship between chordate subphyla

Answer 39

old = U (CV)
new = C (UV)