The pollution from the Industrial Revolution darkening the trees. After the trees darkened from all the soot in the air, the white moths were easier to see and more vulnerable to predators. The dark moths blended into the dark tree bark.
He first divided all living organisms in 2 groups
Animal or Plant
He then put these into subgroups
Animal subgroups: land, water, air
Plant subgroups, small medium or large
Not a very specific approach to taxonomy but it was used for well over 100 years
electricity, chemistry, and astronomy