Prodochordates and Chordate Characters

Question 1

what are chrodates?

Answer 1

bilaterally symmetrical deuterostomes

Question 2

Protostomes (“first mouth”)

Answer 2

spiral (offset cleavage), coelom develops from the splitting of the mesoderm (schizocoelom), blastopore forms mouth

Question 3

Deuterostomes (“second mouth”)

Answer 3

radial (aligned) cleavage, coelom develops of outpouching of gut (enterocoelom), blastopore forms the anus

Question 4

How many sub-phylums does Phylum Chordata have? what are they?

Answer 4

3 subphyla: cephalochordata, vertebrata, urochordata

Question 5

what are the six chordate synapomorphies?

Answer 5

notochord, dorsal hollow nerve cord, pharyngeal slits, myomeres, postanal tail, endostyle

Question 6

notochord

Answer 6

hydrostatic organ with elastic properties that resist axial compression. Largely replaced by the vertebral column in vertebrates. nucleus pulposus in mammals.

Question 7

dorsal hollow nerve cord

Answer 7

induced by the notochord the notochord, develops into the nervous system in vertebrates through neurulation. In non-chordates it is ventrally placed and solid

Question 8

pharyngeal slits

Answer 8

series of small openings that pierce the pharynx.

Question 9

postanal tail

Answer 9

posterior extension of the body past the anus used for locomotion, defense, counter-balance etc.

Question 10

endostyle

Answer 10

involved in mucus production and/or iodine metabolism

Question 11

myomeres

Answer 11

muscle blocks involved in locomotion

Question 12

what function do pharyngeal slits serve in protochordates?

Answer 12

food suspended in water enters the pharynx, food gets trapped in mucus, water exits through the pharyngeal slits

Question 13

what function do pharyngeal slits serve in vertebrates?

Answer 13

the pharynx develops a series of pouches (in place of slits) during embryonic growth. this is an exaptation for respiratory exchange (walls of the pouches become vascularized for gas exchange)

Question 14

Where is the endostyle found in protochordates?

Answer 14

on the pharyngeal floor that produces mucus to trap food and synthesizes iodine binding proteins

Question 15

what is the endostyle homologous with in vertebrates?

Answer 15

the subpharyngeal gland and thyroid gland (synthesizes iodine binding proteins)

Question 16

Protochordates

Answer 16

informal group consisting of hemichordates, cephalochordates, and urochordates, have 1 or more chordate character at some point in devrlopment

Question 17

what type of feeders are protochordates?

Answer 17

passive suspension feeders, using cilia and mucus

Question 18

Hemichordates (acorn worms)

Answer 18

posess pharyngeal slits (not a chordate) that is used to get rid of excess water, uses a ciliated proboscis for locomotion and feeding

Question 19

How many chordate characters do cephalochordates posses?

Answer 19

all 6

Question 20

what function does the ciliated wheel organ serve in branchiostoma?

Answer 20

the ciliated wheel organ draws in water and food particles (then sorted by buccal cirri and velum)

Question 21

what function does hatschek’s pit serve in branchiostoma?

Answer 21

mucus secretion and possible endocrine function

Question 22

What is the oldest known cephalochordate?

Answer 22

Pikaia gracilens (508 MYA)

Question 23

How many chordate characters do ascidian larvae have?

Answer 23

5, 6 including weak myomeres

Question 24

How many chordate characters do adult urochordates have?

Answer 24

2

Question 25

what are adhesive papillae used for?

Answer 25

they are used by ascidian larvae to attach to suitable substrate

Question 26

What is the function of the statocyst?

Answer 26

to sense gravity

Question 27

what is the function of the ocellus?

Answer 27

to sense light

Question 28

what is the auricularian hypothesis of chordate evolution?

Answer 28

started with echinoderm larvae, multiple occurrences of paedomorphosis eventually evolved chordates

Question 29

how many sets of genes specify the dorsoventral axis of the body?

Answer 29

2 sets, code for proteins with a prominent role in dorsal-ventral patterning

Question 30

In echinoderms and Hemichordates, which protein determines the dorsal surface?

Answer 30

BMP (bone morphogenetic protein)

Question 31

In echinoderms and hemichordates, which proteins determine the ventral surface?

Answer 31

chordin