2021年12月07日家庭版托福阅读真题+题目+答案：The Economic and Cultural Impact of Plant Diseases

2021年12月07日托福阅读真题+题目+答案：The Economic and Cultural Impact of Plant Diseases

Plant diseases have affected people for as long as humans have grown crops. ⬛ The ancient Romans even had a god, Robigus, whom they needed to placate in hopes of preventing wheat rust, a disease caused by a fungus that affects wheat, barley, and rye stems, which can cause a significant decrease in crop yield. ⬛ Probably the most famous example of a plant disease was the late blight of potatoes, which devastated the potato crop in Europe and especially Ireland in the mid-nineteenth century. ⬛ A large proportion of the people in Ireland were completely dependent on potatoes for subsistence, and as a result of the blight, Ireland lost about a quarter of its population to famine and emigration. ⬛ It is now known that plant diseases are caused by the same types of organisms, or pathogens, that cause human and animal diseases, including bacteria, fungi, and viruses.

1.In paragraph 1, why does the author mention a Roman god?

O To show that early Romans had little scientific knowledge of crop diseases

O To explain why gods had a significant role in ancient Roman society

O To emphasize that wheat, barley, and rye were particularly important crops in ancient Rome

O To illustrate the length of time plant diseases have seriously affected humans

The discovery of evidence that plant diseases are caused by microscopic organisms was contemporary to discoveries substantiating the theory that infectious animal diseases are caused by microbes. In 1878, fire blight, a disease of pears and apples, was determined to be caused by a bacterium, a discovery that came only two years after the German physician Robert Koch had confirmed that anthrax, a disease of livestock, is caused by a bacterium. The first evidence that infection with a virus, a pathogen smaller than bacteria, can result in disease came from an experiment with the tobacco mosaic virus, which can infect tobacco as well as tomato plants. The experiment, which was performed in the 1890s, showed that sap from a diseased tobacco plant was still infectious after having been passed through a filter with pore sizes small enough to prevent passage of bacterial cells.

2.According to paragraph 2, how did scientists know that tobacco mosaic was caused by a virus?

O Sap from diseased plants still infected other plants after all bacteria had been removed.

O Scientists were able to observe the tobacco mosaic virus by filtering it out of diseased sap.

O The behavior of tobacco mosaic was very different from the behavior of bacterial diseases such as fire blight and anthrax.

O Tobacco mosaic was similar to a disease in tomato plants that was known to be caused by a virus.

Some plant pathogens, such as the organism responsible for cedar-apple rust, must infect an intermediate, or alternate, host before they can complete their life cycle on the economically important host (in this case the apple). For this disease, the alternate host is red cedar, on which the fungus overwinters. Therefore, the elimination of red cedar trees was advocated to help reduce the incidence of the disease. These kinds of relationships with intermediate hosts are not unique to agents infecting plants. Both yellow fever and malaria require an incubation period of roughly ten days in the mosquitoes that transmit them before infection of new human hosts can occur.

3.The word “advocated'' in the passage is closest in meaning to

O ordered

O researched

O attempted

O encouraged

4.All of the following statements about cedar-apple rust are supported in paragraph 3 EXCEPT:

O It is caused by a fungus.

O It negatively affects the production of apples.

O It spends the winter on red cedar trees.

O It kills the red cedar trees that it infects.

。。。。。余下托福阅读真题及题目答案省略！

2021年12月07日家庭版托福阅读真题+题目+答案：The Economic and Cultural Impact of Plant Diseases，10元有偿下载本篇完整版！