7.3 - Circulatory system of a mammal

• Why do large mammals need mass transport systems ?

  Have a higher surface area to volume ratio so have longer diffusion paths, diffusion would take too long
• 4 common features of transport systems ?

  • A suitable medium to carry materials
  • material is moved over large distances, faster than diff
  • use tubular vessels that have branching networks
  • require a mechanism for movement eg. pressure difference
• Why does oxygenated blood have to return to the heart from the lungs, rather than going straight to the body ?

  Loses pressure in the lungs so goes back to heart increase pressure