transport in animals

• function is to transport oxygen and nutrients to cells and transporting waste products away from cells to excretory organs
• Larger organisms need it as diffusion of glucose and oxygen is not fast enough so they need to carried close to the cells
• Smaller unicellular organisms have a large enough surface area to volume ratio for diffusion of gases to be effiecient
• Open Blood System:

  • direct exchange between materials and blood
  • few vessels as it is pumped at a low pressure
  • haemocoel - vessels all open into a common cavity
  • only efficient for small organisms eg insects
• Closed Blood System:

  • Blood is never in direct contact with cells
  • materials never exit blood vessels
  • blood vessels branch into fine capillaries
  • earth worms, squid, octopus, and animals
• Why is a closed blood system more efficient


  • less blood is needed but there are quicker and higher levels of distribution
  • oxygenated blood reaches extremities quicker
  • metabolism, movement, digestion and elimination of wastes is quicker
  • efficient distribution of antibodies so immune response is stronger, this is because blood can be directed to specific area via the vessels