exchange surfaces

• | surface area to volume ratios

  
• | single cellular organisms & exchange surfaces

  • in single celled organisms, gases can diffuse into the cell due top their LARGE SURFACE AREA compared to their volume so enough can be exchanged to supply the volume of the cell
• | multicellular organisms need exchange surfaces

  • multicellular organisms have a SMALLER SURFACE AREA compared to volume; not enough substances diffuse to supply their volume
  • exchange surfaces are ADAPTED to maximise effectiveness:
  • thin membranes: substances have short distances to diffuse
  • large surface area: lots of substances can diffuse at once
  • lots of blood vessels: get stuff in & out of blood quickly