Theory of acquired character was given by Lamarck also called Lamarckism. Mutational theory of evolution was given by Hugo de Vries which states that sudden inheritable change is the cause of evolution.

Industrial melanism was highlighted by Biston betularia. It is an excellent example of natural selection during post industralisation period, the tree trunks become dark due to industrial smoke and sorts. Under these conditions the white winged moth did not survive due to predators (dark-winged or melanised moth). Before industrialization set in, thick growth of almost white-coloured lichen covered the trees.

In that background, the white winged moth survived but the dark-coloured moth were picked out by the predators. Hence, moths that were able to camouflage themselves, i.e., hide in the background, survived. This understanding was supported by the fact that in areas, where industrialization did not occur, $e . g .$, in rural areas, the count of melanic moths was low. Remembers that no variant was completely wiped out