3.3.1 - Surface area: Volume Ratio

Thursday 7th December ‘23

Can I remember SA and V content from GCSE maths?

• Surface area: the amount of space on the outside of a 3D shape

  • height X width X number of faces

• Volume: the amount of space inside a 3D shape

  • height X width X length

How is it calculated?

Divide both sides by the volume resulting a ratio of SA:1

How is this relevant to living things?

• All organisms need to exchange substances with the environment to survive eg oxygen / urea / carbon dioxide.

• Temperature and water levels also need to be kept constant, so heat and water also need to be exchanged.

• Rate of exchange depends on SA in contact with the surroundings.

• Unicellular organisms

  • Have large SA:V.

  • Diffusion distance is short.

  • Can exhange materials directly with their environment.

  • Lose heat energy and water very qyuuck, cannot survive extreme heat or cold.

• Multicellular organisms

  • Have small SA:V.

  • Diffusion distance is large.

  • Lose less energy as heat, have survival advantage.

  • Need internal mass transport systems.