2. 考研
  3. Biological diversity—or biodiversity—is the term given to total variety and complexity and interactions of all life on Earth. Th

Biological diversity—or biodiversity—is the term given to total variety and complexity and interactions of all life on Earth. Th

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问题     Biological diversity—or biodiversity—is the term given to total variety and complexity and interactions of all life on Earth. The biodiversity we see today is the result of billions of years of evolution, shaped by natural processes and, increasingly, by the influence of humans. It forms the web of life of which we are an integral part and upon which we so fully depend.
【C1】______
    In the last 50 years we have lost 300,000 species. Species are disappearing between 100 and 1,000 times as fast as they were before humans arrived. One in four mammal species and one in eight bird species face a high risk of extinction in the near future and the population of each species is expected to fall by at least a fifth in the next 10 years.
【C2】______
    There are a number of factors that threaten biodiversity and the vast majority of them are attributable to human activity.
    There is less and less wilderness in the world. An increasing human population is taking up ever more land for agriculture and accommodation.
    After habitat loss, the biggest threat to biodiversity is invasion by non-native species. These non-native species have arrived mainly through trade and tourism.
【C3】______
    Another threat comes from the illegal trade in wild animals and plants. According to some authoritative sources, the international illegal trade in wildlife is worth an estimated ￡ 5 billion a year. It is second only to the narcotics trade. According to their research, some 500 million animals and plants are traded across borders each year, a quarter of them illegally.
    Given the fact that trade in wild animals and plants crosses borders between countries so international cooperation is needed to safeguard certain species from over-exploitation. CITES helps coordinate this effort.
    CITES or the Convention on International Trade in Endangered Species of Wild Fauna and Flora is an international agreement between governments. Its aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
【C4】______
    Other threat to biodiversity include the pet trade. It is estimated that nine out of ten parrots imported for the pet trade come from the wild. In addition, disease, hunting, pest control, pollution, human eating and the keeping of domestic animals.
    The good news is that people have realized the serious consequences resulting from inappropriate human activity.
【C5】______
[A]Invertebrates aren’t faring so badly—only around 0. 1 percent of the 1. 6 million known species are thought to be threatened—but it’s possible that many undiscovered species will die out before we even know of their existence.
[B]The World Health Organization estimates that more than 60 percent of the world’s population relies on plants for primary healthcare. There are 3,000 plant species used in birth control alone. With great demand for medicine, many herbs, some of which are rare plants, have been killed out.
[C]World leaders have agreed a comprehensive strategy for "sustainable development", that is meeting our needs while ensuring that we leave a healthy and viable world for future generations. They have reached a consensus that the world’s ecological richness should be preserved as nations further their economic development.
[D]Deplorably, biodiversity is being undermined.
[E]Today, it accords varying degrees of protection to more than 30,000 species of animals and plants, whether they are traded as live specimens, fur coats or dried herbs.
[F]The Galapagos Islands have almost as many introduced species as native ones. Invasive plant species already cover 400,000 sq km of the U. S., and are spreading at a rate of 12, 000 sq km a year. Non-native species alter habitat by changing the vegetation, competing with native species, and preying on native species.
[G]Rural communities in more than 60 countries get much of their protein from wild animal meat. Overpopulation, famine and the spread of high-powered rifles are killing off this source of food and people are going hungry.
【C3】
选项
答案F
解析 参照上下文，可知此处应该还是在讲上段提出的问题。此项通过数字说明外来物种的侵入所带来的严重后果，它们与原来的物种争抢食物，甚至将后者消灭，最终改变了原物种周围的植被和生活环境。
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