Lecture 2

Question 1

What does ‘Amphioxus’ mean?

Answer 1

Sharp at both ends.

Question 2

What subphylum are lancelets in?

Answer 2

Cephalochordata.

Question 3

Describe what lancelets are

Answer 3

They are very small, harvested for food in China and burrow by wriggling rapidly.

Question 4

What kind of feeders are lancelets?

Answer 4

Filter feeders.

Question 5

Describe how lancelets draw lancelets in

Answer 5

Water is brought in through the mouth and forced into the perforated pharynx. This is where particulate material e.g. diatoms are removed.

Question 6

Describe the body of a lancelet

Answer 6

Metameric, segmented and has v-shaped muscles.

Question 7

What are the v-shaped muscles in lancelets called?

Answer 7

Myotomes/myomeres

Question 8

What is the lancelet lacking in?

Answer 8

A brain and vertebral column

Question 9

What do buccal cirri do?

Answer 9

Traps unwanted particles

Question 10

Describe the pathway of food

Answer 10

The bars move mucous laden stuff to the blind end of the caecum. Then to the protogut where it’s dissolved and used. Exits via anus.

Question 11

What is buccal pumping?

Answer 11

Changes presure in the oral cavity.

Question 12

What is the pathway of the water?

Answer 12

Pharynx, atrium then the atriopore.

Question 13

Lancelets do respiration through diffusion, true or false?

Answer 13

True

Question 14

Are the atriopore and anus to different openings?

Answer 14

Yes

Question 15

Describe the movement of the vascular system in lancelets

Answer 15

Contractions at different parts of the body move the blood around. They don’t have hearts.

Question 16

Describe the nervous system of lancelets.

Answer 16

They do not have a brain, although they have a cerebral vesicle. Muscles send out extensions to the nerve cord rather than the other way around.

Question 17

What are the mesoderm derived cyrtopodocytes?

Answer 17

They link the vascular system and the atrium. In place of the kidney.

Question 18

What do the sea squirts have that make them urochordates (subphylum)?

Answer 18

The endostyle and pharynx with slits (adult).

Question 19

Describe the larval stage of sea squirts/ascidiacea

Answer 19

They have to find a substrate within minutes to days otherwise they will die.

Question 20

What chordate features do sea squirt larvae have?

Answer 20

Notochord, nerve cord and tail.

Question 21

Describe ascidiacea metamorphosis.

Answer 21

Attaches to substrate with adhesive papillae (secretes mucous), notochord reabsorbed, N.S changes in structure/location. Viscera rearranges: Larval mouth -> inhalent siphon & atriopore -> exhalant siphon. Pharynx expands and gonads develop.

Question 22

What is the function of the cerebral ganglion?

Answer 22

Controls movement, for light sensing organs.