Define homeostasis.

Homeostasis refers to the mechanisms through which living organisms regulate their internal environment to maintain stable, constant conditions despite external changes. This internal stability is vital for the proper functioning of cells and, consequently, the entire organism. For instance, humans maintain a relatively constant body temperature, pH level, and glucose concentration, allowing physiological processes to occur optimally.

The concept encompasses a variety of processes, including thermoregulation, osmoregulation, and blood sugar regulation. When an external temperature fluctuates, for example, the body responds in ways that help maintain a core temperature around 37 degrees Celsius.

Other choices refer to different biological concepts: evolution involves changes in species over generations, growth and development describe how organisms increase in size and complexity over time, and adaptation relates to changes that help organisms survive in different environments. These distinctions highlight why the maintenance of a stable internal environment is specifically linked to homeostasis.