Surface Area to Volume Ratio


This explains why different animals have evolved different transport and gas exchange systems.

Surface Area to Volume Ratio

Specification Reference

"Understand how surface area to volume ratio affects transport of molecules in living organisms."
"Understand why organisms need a mass transport system and specialised gas exchange surfaces as they increase in size."
  • In single celled organisms diffusion alone is enough to transport substances. This is because they have a large surface area to volume ratio.
  • In larger organisms, animals have a smaller surface area to volume ratio meaning diffusion would not be sufficient. This means that a transport system is required.
  • As animals became larger they develop more specialised gas exchange surfaces. This allows substances to be exchanged efficiently therefore allowing the organisms metabolic demands to be met.