What defines a biological organism's ability to maintain stable internal conditions despite environmental changes?

The ability of a biological organism to maintain stable internal conditions despite environmental changes is known as homeostasis. This process is critical for the survival of organisms, as it allows them to regulate factors such as temperature, pH, hydration levels, and ion concentrations within their cells and body. Homeostasis involves a variety of feedback mechanisms that detect changes in the internal environment and initiate responses to restore balance. For instance, when body temperature rises, mechanisms such as sweating help cool the body down, while shivering can help increase warmth when it drops.

Other concepts listed, such as metabolism, adaptation, and reproduction, are indeed important biological functions but do not directly pertain to the regulation of internal stability. Metabolism refers to the chemical processes that occur within organisms to maintain life, adaptation is the evolutionary process whereby organisms become better suited to their environment, and reproduction pertains to the biological process of producing offspring. All these functions work in support of an organism's overall health and functionality, but homeostasis specifically addresses the internal regulation necessary for survival in varying external conditions.