BRAINCAKEThe Need for Transport Systems
Every cell needs a supply of substances such as oxygen and glucose, and must get rid of wastes such as carbon dioxide and urea. In small organisms these can move to and from every cell by diffusion alone. In large organisms diffusion is far too slow, so a mass transport system is needed.
Three factors decide whether diffusion is enough:
1. Surface area to volume ratio (SA:V)
As an organism gets bigger, its volume increases faster than its surface area, so its SA:V falls. A small organism has a large surface for exchange compared with the volume of cells it must supply. A large organism does not have enough surface to meet its needs.
Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz
BrainCake is free. Make an account in seconds and pick up where this page stops.
More in Circulatory Systems
- Features of a Mass Transport System
- Circulation Systems
- Single Circulation System
- Double Circulation System
- Cardiovascular System
- Components of Blood
- Plasma
- Erythrocytes
All 33 lessons in Circulatory Systems · All Edexcel AS-level Biology topics