Question

Most insecticides attack upon insects on their
A. Digestive system
B. Reproductive system
C. Nervous system
D. Respiratory system

Answer 1

Hint: Insecticides are substances that are used to kill insects that cause harm. Most of the insecticides kill insects on direct exposure but some of them show residual effect. The residual effect is slow but kills the whole insect community. Insects are killed by hacking their consciousness through lethal chemicals both organic and inorganic.

Complete answer: Insecticides are certain substances or chemical agents that hinder or kill insects. Insects form an economically and biologically important community but an excess of them causes harm. Insects are the major pests to crops and destroy large agricultural lands in just a few days. Thus, to control their population in agricultural lands or homes insecticides are used. Insecticides can be organic as well as inorganic chemicals including lethal metals. These chemicals are ingested by insects and circulate in their vessels. Most of the insecticide chemicals act upon the nervous system of insects. This makes them dizzy and unconscious upon exposure to insecticide sprays. Gradually the insects lose their control and their nervous system becomes faulty that directs faulty cell functions leading to death.
Many of the insecticides act on the spot. The insect dies rapidly on exposure to the chemical. Insecticides are also used on eggs and larvae of insects to kill and control the population of insects. Nowadays, plants themselves are being modified and made pest-resistant by incorporating toxin-producing genes. With the help of genetic engineering, many plants have been modified to act as self pest control agents. The insects ingest the plants and die. These toxins act on the digestive tract of insects. The reproductive system cannot be targeted by insecticides as it possesses a threat to the extinction of insect species. Moreover, the respiratory system of insects is very different from large animals. They have a modified type of respiration that makes it difficult to kill them by targeting their respiratory system.
Therefore, the correct answer is option C.

Note: Although insecticides are very beneficial in controlling unwanted insect populations. They cause a serious threat to the health of animals as well. As most of the insecticide chemicals get deposited in trophic levels of the food chain, it leads to toxic effects in other animals too. Therefore, an alternative for insecticides is biological control agents. In this, some predator species are used to kill and control the pest insect species.