SA : V ratio

• Surface Area : Volume ratio is the size of the surface area of the organism in comparison to Its volume
• Volume - length x width x height
• SA - length x width
• Single celled organisms can use diffusion to transport molecules into their bodies from the air.

  This is because they have a relatively large SA : V ratio
• Multicellular organisms cannot rely on diffusion alone because they have a small SA : V ratio

  Due to this they have to create a number of adaptions