Perhaps those light colored moths had other characteristics that allowed them to escape the predators. Additionally, there is variety in a species and additional white moths might still be born. Larger number of the dark-colored variety were present in the polluted environment because the dark colored moths would blend in with the polluted trees and therefore be camouflaged for survival.
<span>The purpose of the scientific method is to clearly do an experiment by a process of steps helping you keep track, and correct any mistakes.</span>