Adaptation is the characteristic of living organisms. It includes structural and functional features which improve their chances of survival in the environment in which they live. An organism which copes well with a particular environment leads a better life and breeds more successfully than the one which does not do so. A desert rat is better adapted to living in the desert than a field rat, because the former can cope with harsh conditions of the desert without much discomfort. Similarly, the camel is able to survive and reproduce in deserts better than a water buffalo. The desert rat and the camel are the examples of adaptations to xeric or dry, habitats.

Adaptations may be of two types: 1. Short-term adaptations and 2. Long-term adaptations. Short-term adaptations include those changes which are of temporary nature. For example, when we are exposed to direct sunlight, our skin becomes tanned. Here the skin pigment (melanin) accumulates in the top layer of the skin. This absorbs excess radiation and protects the underlying tissues from harmful effects. Long-term or permanent adaptations can be seen in various birds where the structure of beaks and claws are modified.