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  3. The balance of nature is a delicate system of checks and counter-checks. Nature has its own way of checking the life and distrib

The balance of nature is a delicate system of checks and counter-checks. Nature has its own way of checking the life and distrib

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问题     The balance of nature is a delicate system of checks and counter-checks. Nature has its own way of checking the life and distribution of the different organisms and helping their growth. An epidemic may be considered nature’s way of checking population growth. Man in his attempt to conquer nature and to utilise it to his advantage has interfered with the balance of nature, thereby creating problems of a complex nature. Nature’s ways of maintaining the balance are intricate and not easily understood and man’s application of his scientific knowledge and techniques has upset this balance so much that today, being aware of the disastrous consequences, he takes measures against them.
    No animal or plant can live in isolation, for different organisms are parts of a vast dynamic complex of living things. As no man. or community is serf-sufficient, no organism can live by itself. When man interferes with the interdependence and interrelationships of the different organisms, he is, in effect, upsetting their balanced relationships and his action can have a chain reaction. If we prevent fish eggs from being deposited in a pond, we are allowing an unchecked growth of weeds. The waterfowl which feeds on tadpoles will look for alternatives, thereby tending to upset these blanced relationships. It is important that for the preservation of beauty in nature the balance of nature is maintained.
    Man for his own survival has to make his peace with plant and animal life, the size and distribution of which he has interfered with. It is to be noted that in every plant and animal community there is a trend towards a balance between the different species. When each successive species is of. the right number to maintain a constant population, a balance between the different species is maintained and this state is referred to as the climax stage. Man is forever upsetting the balance of the climax stage. He has added to the numbers of animals and plants that are useful to him. In the process he has unwittingly helped the increase in the number of insects and vermin and as a result he has to wage a relentless war against them. if man continues to interfere with the balance of nature, it is possible that some animals and birds may soon become extinct. The indiscriminate hunting of whales has reduced the number of some species almost to the verge of extinction and international laws have been drawn up to protect them.
    The balance of nature is to be maintained in order to prevent soil deterioration. Human intervention has altered the established relationship between the plants of an area and the soil of that area. Animals introduced by man, sheep and goats for example, have led to widespread soil deterioration. By cutting down trees or by practising unsuitable systems of agriculture, man destroys the crumb structure of soil, thereby making it susceptible to erosion. Soil erosion results in loss of soil fertility and maintaining soil fertility is considered the biggest problem facing mankind apart from the prevention of war. The increase in world population and the growth of civilisation have been the two major factors that have led man to cut down forests on an unprecedented scale and the erosion caused by the cutting down of huge areas of forests has resulted in floods on a scale hitherto unknown. Soil erosion can whittle away soil fertility and if adequate and effective measures are not taken it can become a menacing spectre tearing at the prosperity of many countries.
    Pollution, in its different forms, interferes with the balance of nature.  Water pollution affects nature’s balance in oceans, lakes and rivers. Man-made pollution of water is due to municipal sewage, dumping by factories and the depositing of pesticides. Solid wastes can permeate the soil and pollute lakes and rivers.
    Man has to adopt the philosophy of thrift by conserving natural resources and not destroying them by interfering with the balance of nature. He has to exploit natural resources, taking the environment as a whole. He has to practise fertilization, soil conservation and water management to make a balanced use of the resources of nature possible.
According to the passage, the people’s living of many countries could be seriously threatened by ______.
选项
答案the loss of soil fertility
解析 由题于关键词seriously threatened定位到第四段第五句"Soil erosion results in loss of soil fertility and maintaining soil fertility is considered the biggest problem facing mankind apart from the prevention of war."可知肥沃的土壤是阻止战争的重大问题，如果土壤不再肥沃，战争就可能爆发，世界人民的生活就会受到严重威胁。
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