gas exchange in fish

Question 1

Describe the structure of fish gills

Answer 1

Gill filaments stacked on top of each other.
Gill lamellae project at right angles to the gill
filaments, this increases the surface area of the gills.
The gill filaments and lamellae have a good blood
supply.

Question 2

Describe how a fish
exchanges gases

Answer 2

Water is taken in through the mouth of the fish and
forced out over the gills.through an opening on the
side of the body. Gases are exchanged between the
water and the blood vessels in the gills.

Question 3

Explain the difference
between parallel flow and
counter-current flow

Answer 3

In parallel flow the blood and the water flow in the
same direction. In countercurrent flow the blood and
the water flow in opposite directions.

Question 4

Explain how
counter-current flow
increases the rate of gas
exchange

Answer 4

Rate of gas exchange is increased because
counter-current flow maintains a diffusion gradient
between the water and the blood over the whole
length of the gill.

Question 5

explain the process of counter current flow

Answer 5

• water and blood flow in opposite directions
• blood always passes water with a higher concentration of oxygen
• this maintains the diffusion gradient
• along the whole length of the gill filament