All living things are able to maintain stable internal conditions, whether they are unicellular or complex, multicellular organisms. this property is called:

Homeostasis

Living organisms regulate their internal environment to maintain the relatively narrow range of conditions necessary for cellular function. For example, your body temperature should be kept relatively close to 98.6 °F.

There are a number of different strategies, but an easy to see example might be a jackrabbit, this can release heat through the surface of its large, thin ears, and actually increase blood flow to the blood vessels in the ears to cool in hot weather.