Explanation: Denaturation, in biology, process modifying the molecular structure of a protein. Denaturation involves the breaking of many of the weak linkages, or bonds (e.g., hydrogen bonds), within a protein molecule that are responsible for the highly ordered structure of the protein in its natural (native) state.
Darwin called the ability of an organism to survive and reproduce in its environment fitness. Some organisms were fit to do all of these things, whereas others were not.