Define homeostasis.

Homeostasis refers to the mechanisms that organisms use to maintain a stable internal environment, despite changes in external conditions. This process is vital for the proper functioning of biological systems, as it ensures that factors such as temperature, pH, hydration, and electrolyte levels remain within optimal ranges. For example, when the body temperature rises, mechanisms such as sweating and increased blood flow to the skin help cool the body to maintain a stable temperature. Similarly, if an organism becomes dehydrated, mechanisms will activate to conserve water and maintain hydration levels.

The other options describe different biological processes that do not pertain to the regulation of internal conditions. The process of cell division is crucial for growth and reproduction, stabilization of external environments does not convey the internal consistency required for life, and the breakdown of proteins into amino acids involves digestion rather than the maintenance of internal equilibrium. Thus, the correct choice accurately reflects the core concept of homeostasis in living organisms.