Which of the following best describes diffusion in biology?

Diffusion in biology is defined as the movement of molecules from an area of higher concentration to an area of lower concentration. This process is fundamental to various biological functions, including the transport of substances across cell membranes. It occurs spontaneously and does not require energy, making it a passive transport mechanism.

For example, in the case of gas exchange in the lungs, oxygen diffuses from the alveoli (where its concentration is high) into the blood (where its concentration is lower). Likewise, carbon dioxide moves in the opposite direction during exhalation. This concentration gradient drives the diffusion process, enabling cells to efficiently exchange gases and other essential nutrients.

Understanding diffusion is crucial in comprehending how substances move in and out of cells, affecting overall cellular function and health. The other options presented do not accurately capture the essence of diffusion, as they pertain to energy acquisition, water absorption by plants (which may involve other processes, such as osmosis), and cell division, none of which directly relate to this specific mechanism of molecular movement.