Answer:
Natural selection
Step-by-step explanation:
Natural selection can be described as the differences in the reproduction and survival strategies of individuals as a results of differences in phenotype.
In a more simple language, natural selection refers to a situation whereby organisms that have favorable trait have higher probability to reproduce. In this process, these traits are transferred to the next generation which gives the organisms the ability to adapt to their environment over a long period of time.
Related examples of natural selection are the peppered moth, the peacock large and colorful tails, and the deer mouse.
Therefore, the concept demonstrated by a decrease in dull coloring of peacock is natural selection.