I think because they have a DNA
The one advantage of using DNS assay to detect maltose production is the formation of a soluble and colored product compound.
The reaction that occurs between maltose and DNS in the assay is a redox reaction (reduction and oxidation) such that maltose gets oxidized and becomes Maltonic Acid while the DNS gets reduced into reduced DNS. The intensity of orange/brown /red color of reduced DNS is proportionately related to the amount of Maltose in the solution.
Answer:
adaptation is what's happening, and the moths changed color to adapt to the new environment.
because of the smoke, the light colored moths were easily spotted and eaten. but they changed color over time to account for that, turning black to make them harder to spot and eat.