gas exchange

• most gas exchange surfaces have two things in common:

  1. a large surface area
  2. thin for a short diffusion pathway organism will also maintain a steep concentration gradient of gases
• single celled organisms absorb and release gases by diffusion through their outer surface
• single celled organisms have a large surface area to volume ratio, a thin surface and short diffusion pathway. there's no need for a gas exchange system as oxygen can take part in biochemical reactions as soon as it enters the cell