SA : V ratio

• Surface area to volume ratio decreases as organisms get larger
• Organisms with high SA:V, can rely on diffusion to exchange everything they need
• Organisms with low SA:V, can't rely on diffusion to exchange everything they need, therefore they have specialised exchange surfaces
• As organisms get larger the diffusion distance increases massively, meaning diffusion will be slower and the organism can not depend on it. As a result larger organisms have transport systems, e.g. circulatory system .
• Exchange systems - get substance in and out of the body of organisms
• Transport systems - transport the substances to the parts of the body that need them