3.2 gas exchange

• explain two ways in which the structure of fish gills is adapted for efficient gas exchange

  1. many lamellae increases the surface area which enable efficient gas exchange
  2. thin gills creates a short diffusion pathway
• explain how the counter current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills.

  water and blood flow in opposite directions

  bloood is always passing water with a higher concentration of oxygen

  diffusion occurs throughout the length of gill