Features of Gas Exchange Surfaces (Cambridge O Level Biology)

• The surfaces where gas exchange occurs in an organism are highly varied
  • Different organisms have evolved mechanisms for getting the gases to the gas exchange surface depending on size, habitat etc.
• All gas exchange surfaces have features in common
• These features allow the maximum number of molecules to be exchanged across the surface in the shortest period of time
• They include:
  • Large surface area to allow faster diffusion of gases across the surface
  • Thin walls to ensure diffusion distances remain short
  • Good ventilation with air so that diffusion gradients can be maintained
  • Good blood supply to maintain a high concentration gradient so diffusion occurs faster

Gas Exchange in the Alveolus Diagram

The alveolus is the gas exchange surface in humans