Surface area

• Calculating surface area to volume ratio [square]

  1. Surface area = 6 x side length^2

  2. Volume = side length^3

  3. Ratio = Surface area / Volume
• As organisms get larger, their surface area to volume ratio falls sharply
• Problem for multicellular organisms


  • Surface area is not large enough for their volume
  • Cells in the center cannot get enough oxygen by diffusion
• How animals have solved the problem

  • Special structures for gas exchange with high surface area (e.g. lungs)
  • Transport system to carry gases around the body