Answer: Adaptation
Step-by-step explanation:
The adaptation is the process by which a species becomes fitted to its environment which is a direct result of natural selection.
The traits that best suits the organism in an extreme conditions and helps in better survival is known as adaptation.
The variation in the species can be favored or rejected based on the condition. If the variation helps in survival of the organism in a better way then it is favored and if it is does not favors its survival then it is not carried further.
The best suited character is adapted and carried forward.