Ans: maintain homeostasis
Homeostasis is any self-regulating process by which biological systems tend to maintain stability while adjusting to conditions that are optimal for survival. It is the stable state of an organism and of its internal environment. Maintenance of homeostasis usually involves negative feedback loops. These loops act to oppose the stimulus, or cue, that triggers them. The stable condition is the condition of optimal functioning for the organism, and is dependent on many variables, such as body temperature and fluid balance, being kept within certain pre-set limits.