Exchanging Surfaces

• Exchange Surfaces


  How easily stuff moves between an organism and its environment depends on its surface area to volume ratio
• Organisms Exchange Substances with their Environment
• Cells can use diffusion to

  1. Take in substances they need

  2. Get rid of waste products
• Substances exchanged by diffusion

  • Oxygen
  • Carbon dioxide
  • Urea
• Surface area to volume ratio (SA:V)

  How easy it is for an organism to exchange substances with its environment
• Calculating surface area to volume ratio

  1. Find surface area

  2. Find volume

  3. Divide surface area by volume
• Organisms


  • Hippo
  • Mouse
• Multicellular organisms have a smaller surface area compared to their volume, so they need exchange surfaces for efficient diffusion
• Exchange surfaces


  • Have a thin membrane
  • Have a large surface area
  • Have lots of blood vessels
  • Are often ventilated
• Exchange surfaces are adapted to maximise effectiveness