GRE Reading Comprehension: JiJing 352-GRE阅读机经352篇 - 5LI3UU7QJ7EGFY47K

Basic population biology demonstrates that widespread use of common nonspecific insecticides must inevitably exacerbate the very problems these insecticides were designed to solve because, in addition to killing "bad" insects (those that eat crops), these insecticides have a "side effect" they also kill "good" insects (those that prey on the bad insects) and indirectly reduce the good insects' birth rate. While insecticide use will decimate both populations equally, the bad insects will rebound much more quickly. In predator/prey systems, predators control the death rate of their prey by eating them, while the prey control the birth rate of their predators by providing nourishment. When population numbers of both decline, therefore, the prey's death rate is dramatically reduced because there are many fewer predators, while the predators' birth rate is dramatically reduced because there is less food and it is harder to find. The birth rate of the prey is much less affected, and thus those insects feeding on crops are capable of rebounding first, then, in the resulting environment that is largely devoid of predators, they reach higher numbers than before.