Plants, like animals, are subject to diseases of various kinds．It has been estimated that some 30,000 different diseases attack our economic plants; forty are known to attack corn, and about as many 题目和参考答案——青夏教育精英家教网—

题目内容

Plants, like animals, are subject to diseases of various kinds．It has been estimated that some 30,000 different diseases attack our economic plants; forty are known to attack corn, and about as many attack wheat．The results of unchecked plant disease are all too obvious in countries which have marginal food supplies．The problem will soon be more widespread as the population of the world increases at its frightening rate．Even in countries which are now amply fed by their agricultural products there could soon be the major crops; the resulting famines(饥荒) could kill millions of people, and the resulting hardship on other millions could cause political upheavals(动乱) disastrous to the order of the world．

Some plants have relative immunity to a great many diseases, while others have a susceptibility to them．A blight (萎菌病) may be but a local infection easily controlled; on the other hand it can attack particular plants in a whole region or nation．An example is the blight which killed virtually every chestnut tree in North America．Another is the famous potato blight in Ireland in the last century．As a result of that, it was estimated that one million people died of starvation and related ailments．

Plant pathologists have made remarkable strides in identifying the pathogens of the various diseases．Bacteria may invade a plant through an infestation of insect parasites carrying the pathogen．A plant can also be inoculated by man．Other diseases might be caused by fungus which attacks the plant in the form of a model or smut or rust．Frequently such a primary infection will weaken the plant so that a secondary infection may result form its lack of tolerance．The symptoms(症状) shown may cause an error in diagnosis, so that treatment may be directed toward bacteria(细菌) which could be the result of a susceptibility caused by a primary virus infection．

How many diseases are known to attack wheat?

A．Around 30000 B．Forty

C．Around 29960 D．Around 40

Unchecked plant disease won't result in_______．

A．food shortages in poor country B．food shortages in rich country

C．increase of world population D．disaster in world politics

What is the main idea of the second paragraph?

A．Some plants have relative immunity to a great many diseases．

B．Some other plants have a susceptibility to a great many diseases．

C．The tolerance of a particular plant changes as the growing conditions change．

D．A blight can be a national infection．

According to the passage, some plant diseases can__________．

A．infect people

B．be prevented by inoculation（接种疫苗）

C．be prevented by killing insects

D．be prevented by improving the growing conditions

Which of the following won’t cause plant disease ?

A．Fungus B．Mold C．Smut D．Rust

【小题1】D

【小题2】C

【小题3】C

【小题4】B

【小题5】A

解析:

【小题1】

【小题2】

【小题3】

【小题4】

【小题5】

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Some of the planet’s most precious animals and plants are disappearing, according to the World Conservation Union (IUCN). The group, based in Switzerland, works with governments and experts to protect threatened species. On September 12, the IUCN released its Red List, a list of species at greatest risk of extinction.

The list includes 41,415 animals and plants. The IUCN says that habitat destruction, hunting and other causes threaten one in four mammals, one in eight birds and one in three amphibians(两栖动物).

Who is to blame?

Scientists believe that 99 percent of threatened species are at risk because of human activity. “We are losing animals and plants at a high rate,” says Julia Marton-LefEevre, director general of the IUCN. “We need to change our behavior.” Warmer oceans and over-fishing are changing sea life. This year for the first time corals(珊瑚) made their appearance on the list. The gharial, a crocodile living in India and Nepal, has lost almost 60 percent of its population in the last 10 years. It is a victim（受害者）of habitat destruction.

Still, the news is not all bad. Thanks to efforts made to protect it, the Mauritius echo parakeet, a bird once endangered, has seen an increase in its population. “This shows that protection methods can work,” says Marton-LefEevre. “That’s the message we want to send to young people.”

In China the new reserve（保护区）itself is part of green efforts that have seen more than 2,400 nature reserves of various kinds being set up, covering more than 15 percent of the nation's land area, official figures showed.

"The country's natural resources(资源) have benefited from conservation," said Lei Guangchun, director of the nature reserve department of Beijing Forestry University. "It is a big increase nowadays compared with other countries." Lei said.

The total areas of China’s natural reserves have covered 1.38 million km2, which accounts for 15.4% of China’s area, higher than both the world average（平均水平） of 11% and the rate in most developed countries.

Li Zhong, an official in charge of the nature reserves office with the State Forestry Administration, thought it was important to increase investment（投资） in such reserves at all levels.

1.What do we know about the IUCN?

A. A union for listing animals and plants on the earth

B. A group of volunteers who are interested in wildlife

C. An organization concerning the protection of rare species' survival

D. A government made up officials, scientists and experts

2.What can be concluded from the passage?

A. All the protection methods can’t work. 　

B. The IUCN does most of the protection.

C. The efforts China makes has paid off.　

D. Enough is done in wildlife protection.

3. Which of the following is not the cause of the disappearance of the animals?

A. Bad weather B. Over-hunting C. Warmer oceans D. Habitat destruction

4.Which of the sentence is NOT true?

A. China has been paying great attention to protecting the natural resources.

B. China has set up a lot of natural reserves.

C. The natural reserves in China cover more than 15 percent of the nation's land area.

D. The rate of China's natural reserves is lower than the average of the world.