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Read the passage carefully. Then choose the correct answer.
 
Since 1800, many species of plants, insects and other living things have become extinct and many more are threatened with extinction. Thus far, scientists have been able to gather data on the number of extinct or threatened species of three classes of animals - birds, reptiles, and mammals.

According to the United Nation's International Union for the Conservation of Nature and Natural Resources (IUCN), more than 40 kinds of freshwater fish have become extinct in the past century in North America. Rivers that once teemed with prized sportfish, such as salmon, have been depleted as people built dams, widened channels, and constructed irrigation networks. Some fish species have been killed off because people released foreign fish species and other animals into the waterways that competed with the native species for food.

Australia, which has long been known as a land of fascinating mammals - particularly the kangaroos and koalas - has also faced some problems. Of the 40 species of the world's mammals that are known to have become extinct during the last two centuries, 18 were native to Australia. Scientists blame the impact of agriculture on natural habitats and the release of foxes and other foreign species.

The southern tip of Africa is home to a unique ecological community called the fynbos, which supports an extraordinary variety of plants - about 8500 species. Many of these species are shrub-like plants that bear tiny flowers of many colors. In the past century, 36 species have become extinct and more than 600 others are at risk of extinction, primarily because people have brought in foreign plants that compete with the fynbos for space and sunlight.

In the Mississippi and St Lawrence river basins of North America, naturalists once identified nearly 300 native species of freshwater clams and mussels. Of these, 21 have become extinct since the late 1800s, and another 120 are at risk of extinction. Scientists say the construction of dams and canals and the pollution of waterways by fertiliser and sewage brought about this rapid decline in shellfish populations.

At first glance, amphibians appear to be a bright spot in the global picture. Only five out of more than 4000 species of frogs, toads and other varieties are known to have vanished in the past century. However, ecologists have recorded massive declines in the populations of amphibians worldwide since the 1970s. Many declines occurred in areas that appear to be undisturbed by human activity.

The global nature of these declines is particularly troubling because it suggests that there is widespread pollution of the atmosphere. Populations may be declining because pollution damages amphibian eggs
before the young can hatch. Many ecologists predict that unless human activities change dramatically, we are likely to lose one-half of the world's species during the next 100 years. Such estimates may appear extreme, but scientists point out that archaeological records show that rapid extinction of species followed the spread of human beings across the globe. And we already know of thousands of plant; and animal species of which only specimens in museums remain. Today's massive and rapidly growing human population is capable of much greater damage.

     
  1. From paragraph 1, what threat is being faced by many species of plants, insects and other living things ?
     
  2. From paragraph 2, how many types of freshwater fish have become extinct in North America ?
     
  3. From paragraph 3, what is the impact of agriculture on natural habitats ?
     
  4. From paragraph 6,
    (a) ' ... amphibians appear to be a bright spot in the global picture.' Explain the phrase 'a bright spot'.
    (b) what is the difference between the disappearance of amphibians and other animals ?
     
  5. From paragraph 7,
    (a) what is the danger predicted by ecologists ?
    (b) what is the condition that will reverse such a prediction ?
    (c) what did the scientists point out about the extinction of the threatened species ?
     
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    Answers
     
  1. The threat of extinction.
     
  2. Forty types of freshwater fish have become extinct in North America.
     
  3. Agriculture has caused extinction of 40 of the world's mammal species over the last two centuries.
     
  4. (a) Something pleasant in the midst of unpleasantness.
    (b) The disappearance of amphibians occurred in areas that appear to be undisturbed by human activity.
     
  5. (a) We may lose one-half of the world's species in the next 100 years.
    (b) Humans changing their activities dramatically.
    (c) The rapid extinction followed the spread of human beings across the globe.
     
 
 
 
 

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