surface area to volume ratio

• surface area of cube = length x width x 6
• surface area of sphere = 4 x pi x r^2
• volume of sphere = 4/3 x pi x r^3
• volume of cube = length x width x height
• fick's law = rate of diffusion ∝ surface area x difference in concentration / thickness of gas exchange surface
• as dimensions increase, both surface area and volume increase
• as dimensions increase, the surface area to volume ratio decreases
• as the surface area to volume ratio decreases:

  • a structure with large surface area is needed to compensate
  • a transport system is needed to move substances between the exchange surface and the tissues