第二篇Putting Plants to Work
Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels for decades. But plants are the real experts: They've been using sunlight as an energy source for billions of years.
Cells in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide, and water into sugars and starches, stored energy that the plants can use. This conversion process is called photosynthesis. Unfortunately, unless you're a plant, it's difficult and expensive to convert sunlight into storable energy. That's why scientists are taking a closer look at exactly how plants do it.
Some scientists are trying to get plants, or biological cells that act like plants, to work as miniature photosynthetic power stations. For example, Maria Ghirardi of the National Renewable Energy Laboratory in Golden, Colo., is working with green algae. She's trying to trick them into producing hydrogen instead of sugars when they perform photosynthesis. Once the researchers can get the algae working efficiently, the hydrogen that they produce could be used to power fuel cells in cars or to generate electricity.
The algae are grown in narrow-necked glass bottles to produce hydrogen in the lab. During photosynthesis, plants normally make sugars or starches. "But under certain conditions, a lot of algae are able to use the sunlight energy not to store starch, but to make hydrogen." Ghirardi says. For example, algae will produce hydrogen in an airfree environment. It's the oxygen in the air that prevents algae from making hydrowww.med126.comgen most of the time.
Working in an airfree environment, however, is difficult. It's not a practical way to produce cheap energy. But Ghirardi and her colleagues have discovered that by removing a chemical called sulfate from the environment that the algae grow in, they will make hydrogen instead of sugars, even when air is present.
Unfortunately, removing the sulfate also makes the algae's cells work very slowly, and not much hydrogen is produced. Still, the researchers see this as a first step in their goal to produce hydrogen efficiently from algae. With more work, they may be able to speed the cells' activity and produce larger quantities of hydrogen.
The researchers hope that algae will one day be an easy-to-use fuel source. The organisms are cheap to get and to feed, Ghirardi says, and they can grow almost anywhere: "You can grow them in a reactor, in a pond. You can grow them in the ocean. There's a lot of flexibility in how you can use these organisms."
36. How do plants relate to solar energy?
A. They are the real experts in producing it.
B. They have been a source of it.
C. They have been used to produce it.
D. They have been using it for billions of years.
37. Scientists study how photosynthesis works because they want to
A. improve the efficiency of it.
B. turn plant sugars to a new form of energy.
C. make green plants a new source of energy.
D. get more sugars and starches from plants.
38. Algae are able to use solar energy to produce hydrogen when
A. they are grown in narrow-necked bottles.
B. there is enough oxygen in the air.
C. enough starch is stored.
D. there is no oxygen in the air.
39. Researchers find it difficult to make algae produce hydrogen efficiently because
A. removing the sulfate slows down the hydrogen production.
B. It is hard to create an airfree environment.
C. It is expensive to remove the sulfate from the environment.
D. the algae’s cells work slowly if there is no oxygen in the air.
40. What does Ghirardi say about algae?
A. They grow faster in a reactor.
B. They will be planted everywhere.
C. They are cheap to eat.
D. They can be a good energy source.
第三篇On the Trail of the Honey Badgers
On a recent field trip to the Kalahari Desert, a team of researchers learnt a lot more about honey badgers (獾). The team employed a local wildlife expert, Kitso Khama, to help them locate and follow the badgers across the desert. Their main aim was to study the badgers’ movements and behaviour as discreetly (谨慎地) as possible, without frightening them away or causing them to change their natural behaviour. They also planned to trap a few and study them close up before releasing them. In view of the animal’s reputation, this was something that even Khama was reluctant to do.
“The problem with honey badgers is they are naturally curious animals, especially when they see something new,” he says. “that, combined with their unpredictable nature, can be a dangerous mixture. If they sense you have food, for example, they won’t be shy about coming right up to you for something to eat. They’re actually quite sociable creatures around humans, but as soon as they feel they might be in danger, they can become extremely vicious (凶恶的). Fortunately this is rare, but it does happen.”
The research confirmed many things that were already known. As expected, honey badgers ate any creatures they could catch and kill. Even poisonous snakes, feared and avoided by most other animals, were not safe from them. The researchers were surprised, however, by the animal’s fondness for local melons, probably because of their high water content. Previously researchers thought that the animal got all of its liquid requirements from its prey (猎物). The team also learnt that, contrary to previous research findings, the badgers occasionally formed loose family groups. They were also able to confirm certain results from previous research, including the fat that female badgers never socialized with each other.
Following some of the male badgers was a challenge, since they can cover large distances in a short space of time. Some hunting territories cover more than 500 square kilometers. Although they seem happy to share these territories with other males, there are occasional fights over an important food source, and male badgers can be as aggressive towards each other as they are towards other species.
As the badgers became accustomed to the presence of people, it gave the team the chance to get up close to them without being the subject of the animal’s curiosity — or their sudden aggression. The badgers’ eating patterns, which had been disrupted, returned to normal. It also allowed the team to observe more closely some of the other creatures that form working associations with the honey badger, as these seems to adopt the badgers’ relaxed attitude when near humans.
41. Why did the wildlife experts visit the Kalahari Desert?
A. To observe how honey badgers behave.
B. To find where honey badgers live.
C. To catch some honey badgers for food.
D. To find out why honey badgers have a bad reputation.
42. What does Kitso Khama say about honey badgers?
A. They show interest in things they are not familiar with.
B. They are always looking for food.
C. They do not enjoy human company.
D. It is common for them to attack people.
43. What did the team find out about honey badgers?
A. There were some creatures they did not eat.
B. They may get some of the water they needed from fruit.
C. They were afraid of poisonous creatures.
D. Female badgers did not mix with male badgers.
44. Which of the following is a typical feature of male badgers?
A. They don’t run very quickly.
B. They defend their territory from other badgers.
C. They are more aggressive than females
D. They hunt over a very large area.
45. What happened when honey badgers got used to humans around them?
A. They became less aggressive towards other creatures.
B. They lost interest in people.
C. They started eating more.
D. Other animals started working with them.
