Gas Exchange In Fish

Question 1

Describe counter-current flow

Answer 1

• blood is always passing water with a high oxygen concentration
• blood and water flow opposite each other in the capillary
• diffusion gradient maintained throughout length (of gill)
• if water and blood flowed in the same direction, equilibrium would be reached, like parallel flow

Question 2

2 ways in which fish gills are adapted for gas exchange

Answer 2

• lamella are thin - short diffusion pathway
• gil filaments and lamella which increase the surface area of fish, increasing the rate of oxygen diffusion