Evolution — BIOLOGY STD 12 Science — Question

Industrial Melanism: Industrial melanism in peppered moth (Biston betularia) is an example of natural selection. In England, 1850s before industrialisation there were more white-winged moths on trees than dark-winged or melanic forms. But after industrialisation, i.e. in 1920, dark-winged moths became more than white-winged moths. This is because during industrialisation, the tree trunks covered by white lichens became dark due to air pollution (dust and soot particles). Due to this, white-winged moths could be easily seen and eaten by the predators as they failed in camouflaging (hide or disguise the presence of a person, animal or object). This shows that in a mixed population, those that can adapt, survive better and increase their population size.
Chemical Resistance: It is another example of natural selection. The excess use of herbicides and pesticides leads to selection of resistant varieties of microbes in very less time. Likewise due to these anthropogenic actions antibiotic resistant bacteria are also appearing now-a-days. The above said industrial melanism and chemical resistance are also examples of evolution by anthoropogenic action. This tells us that evolution is a stochastic process, based on chance events in nature and chance mutation in the organism.