Question

Explain why diffusion alone cannot meet the demands of most multicellular animals but state where diffusion is still necessary in these organisms.

Accepted Answer

Diffusion vs transport system:Most multicellular organisms are too large for transport of substances by diffusion as the rate would be too slow due to the low SA:V ratio & large difusion distancesMulticellular organisms are also more metabolically active so large amounts of oxygen and food would need to be transported, constantly and diffusion is too slow for thatDiffusion occurs in specialised exchange surfaces in organisms such as alveoli and capillaries other than that, substnaces are transported by mass flow

Diffusion Multicellular Organisms Large Transport Slow Explain Meet