gas exchange

Question 1

Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill.

Answer 1

water and blood flow in opposite directions

maintains diffusion gradient of oxygen/ oxygen concentration always higher (in water)

diffusion along length of gill

Question 2

describe the pathway taken by an oxygen molecule from an alveolus to the blood

Answer 2

oxygen diffused across the alveolus epithelium

into epithelium of capillary