Component 3.1 - Gas Exchange In Fish

Question 1

What do gills have to maintain a good oxygen supply?

Answer 1

1) A one way current of water kept flowing by a specialised ventilation mechanism
2) Many folds providing a large surface area over which gases can be exchanged

Question 2

How is ventilation in cartilaginous different to bony fish and what does this mean?

Answer 2

They do not have a special mechanism to force water over the gills, but must keep swimming for ventilation to happen

Question 3

Gas exchange in cartilaginous fish

Answer 3

Blood travels through capillaries in the same direction as the water travels. Which is parallel flow.

Question 4

What is the function of the operculum?

Answer 4

It acts both as a valve, letting water out, and as a pump moving water past the gill filaments

Question 5

What is the 6 stage process of how a bony fish takes in water?

Answer 5

1) The mouth opens
2) The operculum closes
3) The floor of the mouth is lowered
4) The volume inside the mouth cavity increases
5) The pressure inside the mouth cavity decreases
6) Water flows in, as the external pressure is higher than the pressure inside the mouth

Question 6

Why would a fish die out of water?

Answer 6

Out of water the gill lamellae stick together and so there is a smaller surface area and therefore not enough gas exchange can take place for the fish to survive.

Question 7

Gas exchange in bony fish

Answer 7

Water in gill pouches flows between the lamellae - in opposite direction to blood

Question 8

How is counter-current flow more efficient?

Answer 8

Blood always meets water which has a higher oxygen concentration than, so oxygen diffuses into the blood along the whole length of the gill lamellae, giving a higher saturation with oxygen

Question 9

How does carbon dioxide get exchanged in bony fish?

Answer 9

It diffuses from the blood into the water, in bony fish due to the counter-current system it diffuses out of the blood along the whole length of the gill lamellae