Final answer:
An animal that allows internal and external conditions to equalize demonstrates homeostasis, which is the maintenance of a stable internal environment in response to external and internal changes, thus ensuring a dynamic equilibrium within the body.
Step-by-step explanation:
If an animal permits internal and external conditions to be equal, it is showing what is known as homeostasis. Homeostasis is the process by which living organisms maintain a stable internal environment necessary for sustaining life, despite changes in external conditions. The term "equilibrium" in the context of organismal homeostasis refers to the dynamic process whereby internal bodily functions are regulated and maintained within a certain range to achieve a stable state.
Homeostasis involves various regulatory mechanisms that continuously adjust to both internal changes, such as fluctuations in blood glucose or calcium levels, and environmental stresses. Examples of regulation include thermoregulation, which involves maintaining body temperature, and osmoregulation, which involves maintaining water content in the body. Even when an animal appears inactive, it is engaged in ongoing homeostatic processes to preserve a steady condition vital for health and function.