All organisms, including humans, must maintain a baseline of normal functions within their cells, tissues, and organs to survive. This constancy of internal functions is referred to as homeostasis. Homeostatic regulation, however, may be disrupted by a variety of both external and internal stimuli known as stressors. Within limits, all organisms have evolved certain physiological mechanisms to respond to stressors in an effort to maintain homeostasis. The range of changes in the physiology (function), morphology (form), and/or behavior of organisms in response to their environments and potential stressors is regulated by its phenotypicplasticity. Coping with these stressors led to the development of both adjustments (behavioral, acclimatory, and developmental) and adaptations, which are explained in detail in the following sections.