Adaptation

A biological adaptation is an anatomical structure, physiological process or behavioral trait of an organism that has evolved over a period of time by the process of natural selection such that it increases the expected long-term reproductive success of the organism. The term adaptation is also sometimes used as a synonym for natural selection, but most biologists discourage this usage.

Adaptation can be viewed as taking place over geological time, or within the lifetime of one individual or a group.

Organisms that are adapted to their environment are able to: Adaptations are the way living organisms cope with environmental stresses and pressures. One common form of physical Adaptation involves acclimatization. Acclimatization allows the organism to be able to exist in its new environment. Adaptation can be structural or behavioural. Structural adaptations are special body parts of an organism that help it to survive in its natural habitat, for example, its skin color, shape and body covering. Behavioural adaptations are special ways a particular organism behaves to survive in its natural habitat. Physiological adaptations are systems present in an organism that allow it to perform certain biochemistry reactions, for example, making venom, secreting slime, being able to keep a constant body temperature.
 * get air, water, food and nutrients
 * cope with physical conditions such as temperature, light and heat
 * defend themselves from their natural enemies
 * reproduce
 * respond to changes around them

Organisms that are not suitably adapted to their environment will either have to move out of the habitat or die out. The term die out in the context of adaptation simply means a species' death rate excedes its' birth rate for a long enough period for the species to disappear.

It is possible for an adaptation to be poorly selected or become less appropriate or even become on balance more of a dysfunction than a positive adaptation over time; this is known as maladaptation and can apply to both humans and animals in such fields as biology, psychology (where it applies to behaviors and other learned survival mechanisms) and other fields.

There is a great difference between adaptation and acclimation. Adaptation occurs over many generations; it is generally a slow process caused by natural selection. Acclimation occurs generally in a single lifetime and copes with issues that are less threatening. For example, if a human was to move to a higher altitude, respiration and physical exertion would become a problem, but after spending a duration of time in high altitude conditions one will soon acclimate to the pressure and function and no longer notice the change.