Diffusion

Organisms use the process of diffusion to allow useful molecules to enter the cells and remove waste products.

Diffusion is the movement of a gas or solute molecules from an area where there are many to an area where there are few until they spread evenly throughout a space. This movement can occur across a cell membrane or outside of cells.

For example, the high concentration of oxygen in the lung’s air sacs moves to a lower concentration in the blood while carbon dioxide moves from an area of high concentration in the blood to a lower concentration in the air sacs.