The rate of diffusion is influenced by several factors. Three main factors are:
Single-celled organisms, such as amoeba, have huge surface areas for their volume. In other words, they have high surface area to volume ratios. So, they can use diffusion to transport substances in and out of their cell.
Let’s imagine two organisms shaped like cubes. The length of each side is 1 metre for the first cube and 2 metres for the second.
For the first cube, the surface area to volume ratio is 6:1, while for the second cube, the ratio decreases to 3:1. So, as the size of the organism increases, the surface area to volume ratio decreases.
This poses a problem for multicellular organisms whose surface area is insufficient for their cell volume. Many cells are positioned too far from the surface for oxygen to diffuse into them effectively
Multicellular organisms solve this problem in two main ways: