3. Organisms Exchange Substances - Gas Exchange In Fish

Question 1

What are the gills of a fish?

Answer 1

A specialised internal gas exchange surface.

Question 2

What are the gills made up of?

Answer 2

Gill filaments.

Question 3

Where are the gills lamellae found?

Answer 3

At right angles to the filaments.

Question 4

What is the function of the gill lamellae?

Answer 4

To increase the surface area of the gills.

Question 5

What is countercurrent flow?

Answer 5

The flow of water over the gill lamellae and the flow of blood within them are in opposite directions.

Question 6

Explain the principles of the countercurrent exchange system:

Answer 6

• Blood that is already well loaded with oxygen meets water, which has its maximum concentration of oxygen. Therefore diffusion of oxygen from the water to the blood takes place
• Blood with little oxygen in it meets water which has had most, but not all, of its oxygen removed. Again, diffusion of oxygen from the water to blood takes place.

As a result, a diffusion gradient for oxygen uptake is maintained across the entire width of the gill lamellae