1911 Encyclopædia Britannica/Adaptation
ADAPTATION (from Lat. adaptare, to fit to), a process of fitting, or modifying, a thing to other uses, and so altering its form or original purpose. In literature there may be, e.g., an adaptation of a novel for a drama, or in music an arrangement of a piece for two hands into one for four, &c. In biology, according to the doctrine of evolution, adaptation plays a prominent part as the process by which an organism or species of organisms becomes modified to suit the conditions of its life. Every change in a living organism involves adaptation; for in all cases life consists in a continuous adjustment of internal to external relations. Every living organism reacts to its environment; if the reaction is unfavourable, disability leading to ultimate extinction is the result. If the reaction is favourable, its result is called an adaptation. How far such adaptations are produced afresh in each generation, whether or no their effects are transmitted to descendants and so directly modify the stock, to what extent adaptations characteristic of a species or variety have come about by selection of individuals capable, in each generation, of responding favourably, or how far by the selection of individuals fortuitously suitable to the environment, or, how far, possibly by the inheritance of the responses to the environment, are problems of biology not yet definitely solved.