FISH GAS EXCHANGE

Question 1

Why can fish not rely on diffusion alone?

Answer 1

• SA:V ratio is too small to meet their demand

Question 2

Where are the gills located?

Answer 2

• behind the head of the fish

Question 3

Structure of the gills:

Answer 3

Gill filaments which are stacked in a pile have gill lamellae which are at right angles to the filaments

Question 4

Adaptations of gas exchange surfaces:

Answer 4

1. Constant blood supply- high concentration gradient maintained
2. Lots of lamellae- high surface area
3. Single lamellae- flat- high surface area
4. Lamellae are very thin- short diffusion distance

Question 6

What is the counter-current principle?

Answer 6

1) Blood that is already well loaded with oxygen meets water that has its maximum concentration of oxygen, so oxygen diffuses from water to the blood
2) Blood with little oxygen meets water that has less oxygen in it but still more than the blood, oxygen diffuses from water to blood
3) Because of this around 80% of the oxygen available in the water is absorbed into the blood. If the flow of blood and water has been in the same direction this figure would be around 50%.

Question 7

Countercurrent mechanism:

Answer 7

• water and blood flow in opposite directions
• maintains a concentration gradient from water to blood along the entire length of the gill