3.3.4 - Transport Systems

Wednesday 27th March ‘24

• Larger organisms have a smaller SA:V ratio - require specific exchange surfaces and transport systems to carry substances from exchange surfaces to tissues that need them. Whether or not there is a specialised transport medium, and whether it is circulated by a pump depends on:

  • The SA:V ratio.

  • Metabollic rate of organism (how active the organism is).

What are the features of transport systems?

• A suitable medium in which to carry materials, e.g. blood. Normally a water based liquid due to the ability to dissolve substances.

• A form of mass transport in which the transport medium is moved around in bulk over large distances - more rapid than diffusion.

• A closed system of tubular vessels containing the transport medium.

• A mechanism for moving the transport medium within the vessels.

How are mammalian circulatory systems special?

• Closed, double circulatory system.

• Blood travels through the heart twice to maintain pressure. Pressure decreased when goes through lungs - circulation would be too low if passed directly to rest of body.