First 138 words of the document:
Sorcha Vaughan 18/9/2010
Larger organisms require circulatory systems as diffusion is not sufficient to be able to provide all the
organisms cells with oxygen (Large distance for diffusion to occur in order to reach cells in the middle of
the organism therefore diffusion would be very slow).
Also with larger organisms the surface area to volume ratio is smaller compared to smaller organisms
and therefore diffusion would not be sufficient.
Hear lungs called pulmonary system lower blood pressure because it would damage the lungs if it
Heart body called systemic system higher blood pressure because it needs to get around the body
Blood moves around the body via mass flow this is the bulk movement of substances due to a pressure