Answer:
homeostasis
Step-by-step explanation:
Homeostasis is a biological phenomenon in which living organisms maintain a stable internal environment irrespective of the changes in their external environment. This process is key to every other activities pertaining to the survival of an organism.
Hence, according to this question, HOMEOSTASIS is the internal process organisms undergo in order to ensure that their internal conditions stay the same even though their outside environment may change. For example, humans maintain a stable internal temperature despite cold weathers.