Final answer:
In organismal homeostasis, 'equilibrium' refers to the stable internal conditions maintained by an organism despite external or internal changes, ensuring vital functions stay within a certain range.
Step-by-step explanation:
The term equilibrium in the context of organismal homeostasis refers to the state of stability or balance within an organism's internal environment. Despite the constant changes occurring both inside and outside of an organism, homeostasis ensures that internal conditions remain relatively stable. This is achieved by the body making continuous adjustments to maintain vital functions within a specific range, thus achieving a dynamic equilibrium. These adjustments include regulating factors like temperature, pH level, glucose concentration, and other critical biochemical parameters.