As the Industrial Revolution came up, not only did it bring new machinery ideas like factories, along with it came pollution, dirt, long smoke & much more. These drastic changes affected the air which hurts humans ,animals & their environments.
Moths are mostly found in two colors, a dark drown & a light tan which shows the different type of genetic variation around.
With the Industrial Revolution, moths tried to adapt in order to survive so moths became darker to camouflage into trees. Tan moths are now visible from a distance.
Tan moths were now easily spotten & eaten at a faster while darker moths blended in & reproduced giving their offspring their beneficial traits.
Since the industrial revolution affected the moths original gene pool , it changed drastically, now the majority of the moths are brown since they were able to reproduce more and they survive longer.
To conclude, Natural Selection is among moths, the darker moths blend in with the darker environment and they survive longer and they reproduce in a greater number.