现代大学英语 第三册 Unit5 Silent Spring.pptVIP

Lesson 11 – Silent Spring For Reference Question: Why did Carson say the chemical war is never won? Chemicals kill indiscriminately, reduce biodiversity and contaminate the entire environment. They cannot solve the pest problem, for pests can adapt to the chemicals and evolve into super races immune to chemicals, and they can undergo a “flare-back”. The vicious circle will never end until man is killed along with other lives. Lesson 11 – Silent Spring Question: In Carson’s opinion, what led to the insect problem? Nature had built-in checks and balances to hold the varieties of species within bounds. Man’s tampering with nature disturbed the balances. Insect problems arose with the intensification of agriculture—the devotion of immense acreage to a single crop and the spreading of thousands of different kinds of organisms from their native homes. Lesson 11 – Silent Spring Question: What is the difference between the natural spreading of species and the man-assisted process? And how does this process contribute to the pest problem? The natural spreading of the species involves the restraining hand of natural enemies that keep down its numbers in its native land. An alien species is introduced by man into a new territory finds no natural enemies, thus becoming enormously abundant in number. Lesson 11 – Silent Spring Question: What should we do to solve pest problems? We should try to have the basic knowledge of animal population and their relations to their surroundings to promote an even balance, control the power of outbreaks of insects and reduce new invasions rather than seeking new technology to suppress this plant or that animal. Lesson 11 – Silent Spring Question: What is Carson’s contention? Nature is an integral nature. We should promote our knowledge of relation of chemicals and ecology. Before we use chemicals, we should know clearly about their effect on environment and people and make reasonable use of them. Lesson 11 – Silent Spring W