ABSTRACT
Understanding the evolutionary genetic mechanism of organisms’ adaptation to the environment in extreme environments provides a way for systematically and globally revealing the genetic mechanisms of natural selection. Hibernation is a state of inactivity and metabolic depression, a way of “throttling down all the body’s engines.” The state of hibernation is characterized by low body temperature, slow breathing and heart rate, and low metabolic rate. Respiration is a very important activity for all animals and also subject to adaptation. Migration is another way to adapt to global differences in temperature and climate. Many bird species are migrating to optimize their food sources and to ensure the survival of their offspring. Fish living in the deep sea naturally evolved an internal structure through the molecular and cellular levels to counter the high-pressure environment. At the biochemical level, virtually all aspects of cell function and metabolism can be the target of adaptive change in response to environmental stress.
