Chapter 2

Question 1

protochordates include what 3 groups:

Answer 1

1. hemichordates
2. cephalochordates
3. urochordates

Question 2

all protochordates are ——- and feed by the means of —– and —–

Answer 2

marine/cilia/mucus

Question 3

members of the taxa hemichordata are like what?

Answer 3

marine worms

Question 4

hemichordates lack what seen in other chordates?

Answer 4

a notochord and postanal tail.

Question 5

hemichordates are protostomes or deuterostomes?

Answer 5

deuterostomes so the mouth forms opposite to the embryonic bladtopore.

Question 6

Proboscis:

Answer 6

used in both locomotion and feeding and includes a muscular outer wall that encloses a fluid filled coelomic space.

Question 7

the muscular lip of the collar is useful for what?

Answer 7

it can be drawn over the mouth to reject or sort larger food particles. The excess water that enters the mouth then exits through the pharyngeal slits.

Question 8

stomochord:

Answer 8

The stomochord is a flexible, hollow tube found in hemichordates. Stomochords arise in embryonic development as an outpocketing from the roof of the embryonic gut anterior to the pharynx. In adults, they extend dorsally from the pharynx into the proboscis, and serve to communicate with the oral cavity. It retains a narrow connection to what becomes the buccal cavity as well.

Question 9

Pharyngeal slits open into a what?

Answer 9

branchial pouch

Question 10

the circulatory system is presented by 2 principal vessels:

Answer 10

1. a dorsal

2. and a ventral blood vessel is propelled by muscular pulsations in the major blood vessels.

Question 11

(the following are on cephalochordata)

Oral hood:

Answer 11

encloses the anterior entrance to the pharynx and supports an assortment of food processing equipment.

Question 12

Projecting from the free edges of the oral hood are what?

Answer 12

buccal cirri that prevent entrance of large particles.

Question 13

why is the wheel organ called that?

Answer 13

ciliated tracts sweep food particles into the mouth and give the impression of rotation.

Question 14

what is the role of velum and velar tentacles?

Answer 14

they are both involved in sampling and sorting food carried in on entering stream

Question 15

Major ciliated food corridors line the pharynx. the ventral channels is called the ——- and the dorsal channel is the —————

Answer 15

endostyle/ epibranchial groove

Question 16

Hatscheks pit or Hatscheks groove:

Answer 16

seceretes mucus to help collect food particles. It is an invagination in the roof of the oral cavity.

Question 17

excess water goes where?

Answer 17

out the pharyngeal slits to the atrium and finally departs posteriorly via the single atriopore.

Question 18

does the tubular nerve cord of the amphiocus enlarge into a differentiated brain?

Answer 18

no

Question 19

what are the segmental myomeres, v-shaped blocks of muscle along the body used for?

Answer 19

swimming and burrowing.

Question 20

How is the notochord of the amphioxus different than other chordates?

Answer 20

consists of a tranversely arranged series of striated muscle cells. Allows the notochord to become stiff which aids in burrowing.

Question 21

the developmental origin of the cephalochordate notochord is from what?

Answer 21

the roof of the embryonic gastrocoel

Question 22

what are the 2 major ways that circulation in amphioxus departs from that of vertebrates?

Answer 22

1. there is no heart. A swelling at the confluence of the returning veins is because of its location in the circulation generally termed sinus venosus but it lacks any pulsation. Instead the hepatic veins, ventral aorta and others pump blood using specizlied myoepthelial cells in their walls.
2. The second difference from the vertebrate circulatory system occurs in the pharynx. here, several parallels vessels travel in each pharyngeal arch from the ventral to the sorsal aorta rather than the single aorta typical of vertebrates. Furthermore, each primary pharyngeal bar contains a narrow extension of the body cavity, the colelomic space.

Question 23

In some urochordata the pharynx is expanded into a complex straining apparatus called the……

Answer 23

branchial basket

Question 24

what is the mor common name for urochordates “tunicates” inspired by?

Answer 24

the fexible outer body cover, the tunic, secreted primarily by the underlying epidermies.

Question 25

only the —– stage in urochordates exhbits all 5 chordate charactristics simultaneously?

Answer 25

larvae

Question 26

in urochordata water is draw in through what and expelled through what?

Answer 26

drawn in through an incurrent siphon and expelled through the excurrent siphon.

Question 27

where does the anus empty into?

Answer 27

into the excurrent siphone and thuse does not clearly mark the point beyond which the tail continues.

Question 28

otolith:

Answer 28

tiny, marble shaped black spot that is a sensor of gravity.

Question 29

ocellus:

Answer 29

the irregular black spot that is a light sensitive eyespot

Question 30

what disapears when the urchordata becomes an adult?

Answer 30

notochord, tail and dorsal and tubular nerve cord

Question 31

stigmata:

Answer 31

although the pharynx persist and even expands, it becomes high modified and the slits in its wall proliferate and each subdivides repetaedly produced these smaller openings.

Question 32

what are 3 reasons why most protochordates share a common mode of feeding?

Answer 32

1. Given the relatively small size of the larvae and adults, suspended food particles may be the most abundant food source.
2. Each of these protochordates has inherited a system of mucus production and cilia that are well suited for moving currents of water and extracting suspended food.
3. Finally, other feeding systems that chew food typically require hard skeletal systems or tough plates that have not evolved in these groups.