Mosquitoes resistant to the pesticide DDT first appeared in India in 1959, but now are found throughout the world. Graph the data in the table below. Examine the graph, hypothesize why the percentage of mosquitoes resistant to DDT rose rapidly. Suggest an explanation for the global spread of DDT resistance. Solution DDT is an effective broad spectrum insecticide. However, since it is persistant in nature and does not degrade easily, its use is banned in many countries like US. Malarial outbreaks spread by infected mosquitoes are controlled by spraying DDT in the affected areas. DDT sprays are lethal to the mosquitoes in general and immediately declines their growing populations. However, mosquitoes have a short life cycle, they are rapidly multiplying populations. Thus they can undergo beneficial mutations at a faster rate and can quickly develop resistance to the attack of insecticides such as DDT. It is always easier for a species with shorter life span to aquire genetic changes and develop resistance to the changing environment. DDT-resistant mosquitoes which may occur at very low frequency are naturally selected for survival than to DDT-sensitive populations. Thus the given graph shows an exponential increase in the population of DDT resistant mosquitoes..