Question

Why simple diffusion can not help in multicellular organism?

Answer 1

Explanation:

Large multicellular organisms therefore cannot rely on diffusion alone to supply their cells with substances such as food and oxygen and to remove waste products. ... So the larger SA/V ratio of the smaller box would allow more efficient diffusion and exchange of materials

Answer 2

Answer:

As the size of an organism increases, its surface area to volume ratio decreases. This means it has relatively less surface area available for substances to diffuse through, so the rate of diffusion may not be fast enough to meet its cells requirements.

Large multicellular organisms therefore cannot rely on diffusion alone to supply their cells with substances such as food and oxygen and to remove waste products. Large multicellular organisms require specialised transport systems.