The process by which organisms maintain a stable internal environment despite changes in external conditions. This involves feedback mechanisms that regulate body temperature, pH, glucose levels, etc.

A passive process where molecules move from an area of higher concentration to an area of lower concentration. In single-celled organisms, diffusion directly exchanges gases and nutrients with the environment. In multicellular organisms, diffusion occurs across cell membranes and within tissues to distribute oxygen, nutrients, and waste products.

The process by which organisms maintain a stable internal environment despite changes in external conditions.