The excessive use of herbicides, pesticides etc. has resulted in selection of resistant varieties. It is an example of evolution by:

Anthropogenic action

The correct answer is Option (4)- Anthropogenic action

Natural selection, as proposed by Darwin, is a principle stating that nature favors the survival of individuals who are best adapted to their environment, while less adapted individuals are gradually eliminated.

Chemical action refers to the process by which substances interact and transform into different substances through chemical reactions. These reactions involve the making and breaking of chemical bonds, resulting in the formation of new products.

Hugo de Vries, a Dutch botanist proposed mutation theory to explain the mechanism of evolution. According to him, mutations are sudden and heritable changes that are subjected to natural selection. The frequency of a mutated gene in the population is expected to increase if the gene is selected by nature.

Anthropogenic actions refer to activities caused by humans. The excessive application of weedicides and pesticides has driven the evolution of resistant varieties of weeds and pests, respectively. Excessive use or misuse of antibiotics has facilitated the evolution of antibiotic-resistant bacteria.