DDT is used to kill mosquito caterpillar that carries malaria but it affected the ecological balance and the whole food chain in natural ecosystem. houseflies died when they fed on the dead caterpillars. This in turn killed little lizards when they fed on dead houseflies. Finally, the cats that eat the dead lizards died of ddt poisoning. The effect was invasion of dwelling with more and more rats raiding the house for food and carrying the plague. Negative feedback
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Or neither