Cats are common and beloved pets. Litterbox issues are among the most common cha-组卷网 (2025)

【推荐1】A group of scientists trained dogs to detect(发现)a crop disease called citrus greening. The disease has affected orange, lemon and grapefruit trees in the American states of Florida, California and Texas. The dogs can detect the disease weeks to years before it appears on tree leaves and roots, the researchers report. Using dogs is also faster, less costly and more exact than having people collect hundreds of leaves for lab analysis.

Timothy Gottwald is a researcher in the study. He said, “This technology is thousands of years old — the dog's nose. We^’ve just trained dogs to hunt new prey：the bacteria that cause a very damaging crop disease.^”

Citrus greening is caused by a kind of bacteria that are spread by a tiny insect that feeds on the leaves and stems of citrus trees. Once a tree is infected(感染)，there is' no cure. The disease has also hurt citrus crops in Central and South America and Asia. In one experiment involving grapefruit trees in Texas, trained dogs were correct 95 percent of the time in telling the difference between newly infected trees and healthy ones. “The earlier you detect the disease, the better chance you have at stopping healthy trees being infected by removing infected ones,” Gottwald said.

Professor Matteo Garbelotto says the new research shows that dogs can detect an infection well before present methods. He has been involved in similar research but had no part in the new study.

Laura Sims is a plant scientist. She praised the steps taken to find out if the dogs were detecting the bacteria itself or a plant's reaction to an infection. To do that, the researchers infected different kinds of unrelated plants with the bacteria in a laboratory. The dogs were still able to pick out the infected plants.

Gottwald said, "You've seen dogs working in airports, detecting drugs and explosives. Maybe soon you will see them working on more farms."

1. What does the text say about citrus greening?

2. How does a dog detect citrus greening?

3. Early detection of citrus greening enables farmers to ______.

4. Which of the following statements reflects Gottwald's opinion?

相似题 纠错 收藏 详情 加入试卷

名校

【推荐2】In a recent study, researchers at Germany’s Technical University of Munich（TUM）find that trees in cities can grow up 25% faster than their country cousins. This is believed to be a direct result of the heat island effect, which is a situation where the temperature of the city is higher than the nearby rural areas. It’s mostly caused by the fact that buildings, roads, and many other things in the city take in a lot of sunlight and send out the sun’s heat more than natural landscapes such as forests and water bodies. A secondary cause is waste heat produced by heavy uses of energy.

For the study, TUM researchers studied 1,400 trees in 10 cities around the world, which were found in both city centers and nearby rural areas. Based on tree ring study, researchers found that city trees are growing faster than their rural cousins. But before the 1960s, both city and rural trees grew at about the same speed.“We can show that city trees of the same age are generally larger than rural trees because they grow faster. While the difference is about a quarter at the age of 50, it is still just under 20% at a hundred years of age,” lead author Hanz Pretzch says.

Researchers from TUM also found that in some cities, higher-than-normal temperatures have led to growing seasons that are more than eight days longer than the norm. This sounds like a good thing. But while fast -growing city trees are busy taking in CO₂and providing relief from the heat, they’ re also aging and dying at a faster speed than rural trees. As a result, these trees need to be replaced and replanted more frequently.

Considering the valuable “ecosystem services” that city trees provide, planning and management should follow to make a change with today’s tree growth speed. Pretzch and his team set out to perform the study largely in response to United Nation’s report that the world’s cities will experience population growth of more than 60% by 2030. And with such fast growth comes a great need for city trees that make these cities better places to live in.

1. What does the first paragraph mainly tell us?

2. What can we learn from the findings of the research?

3. What is the result of city trees growing faster?

4. Which of the following might be the best title for the text?

相似题 纠错 收藏 详情 加入试卷

名校

【推荐3】It is a question that has long puzzled scientists—exactly why are tigers orange? One might think it makes them more obvious-particularly against a leafy green forest background. William Blake summed it up in his famous poem known by generations of schoolchildren: “Tyger, tyger, burning bright / In the forest of the night.” But now the answer is at hand.

While obvious to us, computer simulations (模拟) of what the big cats look to the main animals they hunt for, deer, show a different picture. Humans with normal colour vision, can see red, blue and green colours. But deer can only pick up blue and green light, they are effectively colourblind to the colour red, like some humans. It means the tigers’ orange colouration looks green to them, allowing them to mix perfectly into the background, new research claims.

Dr John Fennell at the University of Bristol and colleagues said that they used computers to estimate how noticeable a given animal was. They did this by using images of the environment in which the animal lives, and then creating images to see whether the camouflage helps the animal to mix in.

Dr Fennell writes that by simulating what the world looks like to animals who are “two-colour vision”—someone who cannot discover the difference between red and green—“we also identify the most suitable colours for hiding and visibility”.

Dr Fennell writes in the Royal Society Journal Inter face: “Considering the coat of a tiger, it has fur that appears orange to a three-colour vision observer rather than some shade of green, though the latter should be more appropriate color for an attack hunter in forests. However, when viewed as a two-colour vision observer, the tiger’s colour is very effective.”

The question then arises as to why tigers don’t grow green coats. Dr Fennell and colleagues write that mammals (哺乳动物) are not able to produce green fur. To do so would “require a significant change to mammalian biochemistry”. There is only one mammal known to have green fur but this is achieved through what might be considered as, well, cheating, not exactly real.

1. Why does the author mention the poem in paragraph 1?

2. What color is inexistent in the eyes of deer?

3. What does the underlined word “camouflage” mean in paragraph 3?

4. What can be inferred from the last paragraph?

相似题 纠错 收藏 详情 加入试卷