6.3 Gas exchange in fish

Question 1

Describe the structure of the gills

Answer 1

The gills are located behind the head.

They are made up of gill filaments, which are stacked up in a pile like pages in a book.

At right angles to the filaments are gill lamellae, which increase the surface area of the gills.

Question 2

Describe the route by which water moves in regards to the gills

Answer 2

Water is taken in through the mouth and forced over the gills are out through a opening on each side of the body

Question 3

What is the countercurrent flow

Answer 3

Water and blood flow in opposite directions

Question 4

What does the counter-current exchange principle mean

Answer 4

1. Blood that is already well loaded with oxygen meets water, which already has its maximum concentration of oxygen. Therefore diffusion of oxygen from the water to the blood takes place
2. Blood with little oxygen meets water that has had most, but not all, its oxygen removed. Oxygen again moves from the water to the blood

Question 5

What does the countercurrent flow do to the efficiency of the gills

Answer 5

80% of oxygen available in water is absorbed compared to the 50% if it was the samecurrent flow

Question 6

What does the countercurrent flow cause

Answer 6

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