Exchange between organisms and their environment

• Smaller organisms have a larger surface area than volume, so have a large surface area to volume ratio
• Larger organisms have a larger volume compared to their surface area so have a smaller surface area to volume ratio
• Organisms have these features:

  • flattened shape
  • specialised exchange surfaces
• Features of specialised exchange surfaces:

  • large surface area to volume ratio
  • very thin
  • selectively permeable
  • maintains a concentration gradient
  • moist conditions