In Biology, the terms "fitness" and "adaptation" go in hands with hands. Fitness can be defined as the <em>capability of an organism to cope with environmental fluctuations in such a way that it is better able to reproduce and survive in that environment.</em> This process in turn increases the adaptation of an organism for that environment. So adaptation can be considered as the process in which living organisms due to their better fitness acquire some characteristics which help in their improved survival.
The more an organism possesses fitness, the more it will have the adaptations towards adverse environmental fluctuations and ability to survive.
