6.3- GAS EXCHANGE IN FISH

Question 1

What is the outer covering of fish like?

Answer 1

waterproof, and so gas-tight

Question 2

What is the SA:V of fishes like as they are relatively large?

Answer 2

small SA:V

Question 3

Is the body surface of fishes adequate to supply + remove their respiratory gases?

Answer 3

no

Question 4

What specialised internal gas exchange surface have fishes evolved?

Answer 4

gills

Question 5

Where are the gills located in a fish?

Answer 5

within body of fish, behind head

Question 6

What are the gills made up of?

Answer 6

gill filaments

Question 7

How are the gill filaments arranged?

Answer 7

stacked up in a pile

Question 8

What is at right angles to the filaments?

Answer 8

gill lamellae

Question 9

What does the gill lamellae increase?

Answer 9

increase SA of gills

Question 10

What happens to water as it taken through the mouth of the fish?

Answer 10

forced over gills + out through opening on each side of body

Question 11

What is the direction of flow of water over the gill lamellae + flow of blood within them like?

Answer 11

in opposite directions

Question 12

What is it known as, as the direction of water over the gill lamellae + flow of blood within them is in opposite directions?

Answer 12

countercurrent flow

Question 13

What is the countercurrent flow important for?

Answer 13

ensuring maximum possible has exchange achieved

Question 14

What would happen if the water and blood flowed in the same direction in the gill lamella?

Answer 14

far less gas exchange would happen

Question 15

What is the essential feature of the countercurrent exchange system?

Answer 15

blood + water that flow over gill lamellae do so in opposite directions

Question 16

What does the countercurrent exchange system mean: blood that’s already well loaded with oxygen?

Answer 16

blood that’s already well loaded with oxygen meets water, which has max concentration of oxygen
so diffusion of oxygen from water to blood happens

Question 17

What does the countercurrent exchange system mean: blood with little oxygen?

Answer 17

blood with little oxygen meets water which has had most, but not all, of its oxygen removed
so diffusion of oxygen from water to blood happens

Question 18

What is maintained by the countercurrent exchange system?

Answer 18

diffusion gradient for oxygen uptake maintained across entire width of gill lamellae

Question 19

As the countercurrent exchange system maintains the diffusion gradient, how much oxygen is absorbed?

Answer 19

about 80% of oxygen available in water absorbed into blood of fish

Question 20

If the flow of water + blood was in the same direction, what would happen to the diffusion gradient?

Answer 20

diffusion gradient would only be maintained across part of length of gill lamellae

Question 21

If the flow of water + blood was in the same direction, how much oxygen would be absorbed?

Answer 21

only 50% of available oxygen would be absorbed into blood