Physiology is how organs and tissues of the body are structured and working. By evolution, the physiology of all living organisms is designed to keep them healthy and thriving in order to survive and reproduce.
The physiology of any species is specifically adapted to the environment in which the species normally live. Arctic mammals, for example, have a range of adaptations that let them stay year-round in the same habitat instead of migrating to warmer areas in winter. These include thick layers of isolating fat, special lung alveolus allowing them to stay for a long time both below and above water, and delayed implantation. In contrast migrating birds have adaptations to ease long-distance movement, such as hollow bone structure keeping body mass low, long pointed wings, and even doping (yes, like some sport athletes do)!