Transport System

• The circulatory system: needs for transport systems:

  In single-celled organisms such as protists, and small multicellular organisms, essential molecules will move to where they're needed by diffusion.

  Once an organism, eg a very early embryo gets beyond a certain size, it needs a transport system to distribute essential molecules efficiently.

  system
• Features of transport systems

  Common features of transport systems:

  • they are made up of tubes or 'vessels' that carry materials from one part of the organism to another
  • they make close contact with cells, such as those of exchange surfaces
• OXygen is transported from the lungs to all the body cells
• carbon dioxide is transported from all the body's cells to the lungs
• Glucose is transported from the digestive system to the liver and then all the body's cells
• Urea is transported from the liver cells to the kidneys