Restoring the quake­hit ecosystems is a question of balancing the interests of the local people and the environment. Rural methane (沼氣) projects can reduce the number of locals taking firewood from the mountainsides. The use of straw as food for animals will ensure that vegetation(草木) can grow. In Sihai township and Dazhuangke village, in Beijing, they now have a forestry coverage of 85% or more, compared to the 30% they had 15 years ago. Back then, land was used very inefficiently: one person would use 20 mu of forest just for firewood. With those pressures on the ecosystem, no amount of spending on reforestation will succeed. Then the government relocated the population and paid those who remained to tend the forest and provide coal. This reduced the pressures on the ecosystem and it was able to recover naturally.
When an ecosystem has not been pushed past certain limits, it is able to recover on its own. Human involvement should only play a minor role, including after an earthquake. This is particularly the case for sandy grasslands, grasslands deserts, the mountains of the south and the northern sides of mountains in the north. In these areas soil remains and the water, light, heat and nutrients needed are available. Less human involvement is even more appropriate in areas with a small population, where it can avoid money being wasted on ineffective efforts, such as creating forests in dry areas.
The creation of nature reserves should be a model to allow damaged ecosystems to recover. Funding can start at the national level; centrally­funded nature reserves can enforce environmental protection laws and help to promote the local economy. This will solve the problems of reserves being run to make money. When national reserves are funded, local governments will be able to adopt the same model and provide the funds for nature reserves from their own budgets. The first project should be established in nature reserves hit by the quake; these can then become models for other areas.
小題1:To restore the quake­hit ecosystem, government should ________.
A．forbid locals from taking firewood from the mountainsides
B．encourage local people to feed their animals just with straw
C．spend large amounts of money relocating the population
D．protect the environment without harming locals' interests
小題2:The forestry coverage in rural Beijing has increased greatly because ________.
A．pressures on land were reducedB．a(chǎn) large amount of coal is provided
C．no people live in that areaD．locals take good care of the forest
小題3:According to the passage ________ play(s) a major role in ecosystem recovery.
A．local peopleB．nature itself
C．human involvementD．government's effort
小題4:According to the last paragraph, which of the following is NOT true?
A．Nature reserves could be helpful to recover the damaged ecosystems.
B．Centrally­funded nature reserves are beneficial to local economy.
C．Some nature reserves are created for the purpose of making money.
D．The first projects on nature reserves should be set up in quake­hit areas.

小題1:D
小題2:A
小題3:B
小題4:D

試題分析：本文敘述了人們應(yīng)當(dāng)保護(hù)環(huán)境，在一些地區(qū)由于土地的減少，綠地覆蓋率相對的提高了，但是自然的破壞還需要自然自己去修復(fù)，這就需要人們在一些受災(zāi)區(qū)應(yīng)該采取適當(dāng)?shù)拇胧﹣肀Ｗo(hù)生態(tài)環(huán)境，比如可以建立自然保護(hù)區(qū)的方法來使自然恢復(fù)常態(tài)。
小題1:細(xì)節(jié)理解題。根據(jù)Restoring the quake­hit ecosystems is a question of balancing the interests of the local people and the environment. 既要保護(hù)環(huán)境又要顧及人們的興趣，故選D。
小題2:推理判斷題。根據(jù)they now have a forestry coverage of 85% or more, compared to the 30% they had 15 years ago. Back then, land was used very inefficiently: 由于土地的面積減少，使綠地的覆蓋率相對的增加，故選A。
小題3:細(xì)節(jié)理解題。根據(jù)When an ecosystem has not been pushed past certain limits, it is able to recover on its own.自然在生態(tài)環(huán)境的恢復(fù)上起著重要的作用，故選B。
小題4:細(xì)節(jié)理解題。根據(jù)The first project should be established in nature reserves hit by the quake;在地震受災(zāi)區(qū)應(yīng)該建立自然保護(hù)區(qū)，故選D。
考點(diǎn)：
練習(xí)冊系列答案
相關(guān)習(xí)題

科目：高中英語 來源：不詳 題型：閱讀理解

Australian scientists are trying to give kangaroo-style stomachs to cattle and sheep in order to cut he greenhouse gases they send out, which are thought to be responsible for global warming.
Thanks to special bacteria in their stomachs, kangaroo flatulence(腸胃氣脹)contains no methane(甲烷)and scientists want to transfer that bacteria to cattle and sheep who produce large quantities of the harmful gas.
While the usual image of greenhouse gas pollution is a billowing smokestack (煙囪) pushing out carbon dioxide, farm animals’ passing wind contribute a sur­prisingly high percentage of total emissions (排放物)in some countries.
“Fourteen percent of emissions from all sources in Australia are from enteric methane from cattle and sheep,” said Athol Kleve, a senior research scientist with the Queensland state government.
“And if you look at another country such as New Zealand, which has got a much higher agricultural base, they're actually up around 50 percent, ” he said.
Researchers say the bacteria also make the diges­tive process much more efficient and could potentially save millions of dollars in feed costs for farmers.
But it will take researchers at least three years to isolate (分離) the bacteria, before they can even start to develop a way of transferring it to cattle and sheep.
Another group of scientists, meanwhile, has suggested Australians should farm fewer cattle and sheep and just eat more kangaroos.
The idea is controversial (有爭議的), but about 20 percent of health-conscious Australians are believed to eat the national symbol already.
“It's low in fat, it’s got high protein levels and it's very clean in the sense that basically it's the free-range (放養(yǎng)的) animal,” said Peter Amp of the University of New South Wales's institute of environmental studies.
小題1:Scientists intend to put bacteria into cattle and sheep _________.
A．so that they can make full use of special bacteria
B．to help Australian farmers to earn more money
C．so that they can protect Australian ecosystem
D．to prevent them from sending out harmful gases
小題2:Athol Kleve seems to believe that ________.
A．cattle and sheep produce more carbon dioxide
B．less cattle and sheep are raised in New Zealand
C．farm animals are responsible for greenhouse gases
D．New Zealand has the most animals in the world
小題3:What do the underlined words “the idea” in para­graph 9 refer to?
A．Australians should farm fewer cattle and sheep and just eat more kangaroos.
B．The bacteria could make the digestive process much more efficient.
C．Australians should give kangaroo - style stomachs to cattle and sheep.
D．The bacteria could save millions of dollars in feed costs for farmers.
小題4:Which of the statements is the advantage Peter Amp lists about kangaroo?
A．it is rich in protein B．it is cheaper than beef
C．it is high in fatD．it is more delicious than sheep

查看答案和解析>>

科目：高中英語 來源：不詳 題型：閱讀理解

Antidepressant（抗憂郁）drugs such as Prozac were viewed in the early 1900's as wonder pills that would remove depressive blues for good. But in the past five years, growing scientific evidence has shown these drugs work for only a minority of people. And now a research journal says that these antidepressants can make many patients' depression worse. This alarming suggestion centres on the very chemical that is targeted by antidepressants-serotonin（血清素）. Drugs such as Prozac are known as selective serotonin re-uptake inhibitors（or SSRIs）. Their aim is to increase the level of this  “feel-good” chemical in the brain.
But the new research, published in the journal Frontiers In Evolutionary Psychology, points out that serotonin is like a chemical Swiss Army knife, performing a very wide range of jobs in the brain and body. And when we start changing serotonin levels purposely, it may cause a wide range of unwanted effects. These can include digestive problems and even early deaths in older people, according to the study's lead researcher Paul Andrews. “ We need to be much more cautious about use of these drugs,” says Andrews, an assistant professor of evolutionary psychology at McMaster University in Ontario, Canada.
Previous research has suggested that the drugs provide little benefit for most people with mild depression, and actively help only a few of the most severely depressed. Famous psychologist Irving Kirsch has found that for many patients, SSRIs are no more effective than a placebo pill. A research in 2010 on Danish children found a small, but significant, increase in the risk of heart problems among babies whose mothers had used SSRIs in early pregnancy. The key to understanding these side-effects is serotonin, says Andrews. Serotonin is also the reason why patients can often end up feeling still more depressed after they have finished a course of SSRI drugs. He argues that SSRI antidepressants disturb the brain, leaving the patient an even greater depression than before.
“After long use, when a patient stops taking SSRIs, the brain will lower its levels of serotonin production,” he says, adding that it also changes the way receptors in the brain respond to serotonin, making the brain less sensitive to the chemical. These changes are believed to be temporary, but studies indicate that the effects may continue for up to two years.
Most disturbingly of all, Andrews' review features three recent studies which, he says , show that elderly antidepressant users are more likely to die earlier than non-users, even after taking other important variables into account. One study, published in the British Medical Journal last year, found patients given SSRIs were more than 4 per cent more likely to die in the next year than those not on the drugs.
“Serotonin is an ancient chemical,” says Andrews. “It is regulating many different processes, and when you disturb these things, you can expect that it is going to cause some harm.”
Stafford Lightman, professor of medicine at the University of Bristol, and a leading UK expert in brain chemicals and hormones, says Andrews’ review highlights some important problems, yet it should also be taken with a pinch of salt. “This report is doing the opposite of what drug companies do,” he says. “Drug companies selectively present all the positives in their research, while this search selectively presents all the negatives that can be found. Nevertheless, Andrews' study is useful in that it is always worth pointing out that there is a downside to any medicine. ” Professor Lightman adds that there is still a great deal we don't know about SSRIs-not least what they actually do in our brains.
When it comes to understanding why the drugs work only for a limited part of patients, U.S.  scientists think they might now have the answer. They think that in many depressed patients, it’s not only the lack of feel-good serotonin causing their depression, but also a failure in the area of the brain that produces new cells throughout our lives. This area, the hippocampus, is also responsible for regulating mood and memory. Research suggests that in patients whose hippocampus has lost the ability to produce new cells, SSRIs do not bring any benefit.
小題1:According to paragraph 2, serotonin, like a chemical Swiss Army knife, can             .
A．make many patients' depression worse
B．cause a wide range of unwanted effects
C．a(chǎn)ffect human body and brain in various ways
D．provide little benefit for most depressed people
小題2:In Stafford Lightman's opinion,                    .
A．drug companies don't know the negative effect of antidepressants
B．Andrews focused on different things from the drug companies
C．scientists have found what SSRIs do in the brain
D．Andrews' research has no medical value
小題3:Which of the following is TRUE about SSRIs?
A．They are used to increase the “feel-good” medical in the brain.
B．They can work even when the hippocampus can't produce new cells.
C．They create a risk of heart problems in pregnant women.
D．They are responsible for controlling mood and memory.
小題4:What is the text mainly about?
A．The aim of drug companies
B．The function of SSRIs
C．The side-effects of antidepressants
D．The cause of depression

查看答案和解析>>

科目：高中英語 來源：不詳 題型：閱讀理解

The computer keyboard helped kill shorthand---a system of rapid handwriting, and now it's threatening to finish off handwriting as a whole. When handwritten essays were introduced on the SAT exams for the class of 2011, just 15% of the most 1.5 million students wrote their answers in cursive (草寫字母）.The rest? Block letters.
And those college hopefuls are just the first edge of a wave of US students who no longer get much handwriting instructions in the primary grades, frequently 10 minutes a day or less. As a result, more and more students struggle to read and write cursive.
At Keene Mill Elementary School in Springfield, all their poems and stories are typed. Children in Fairfax County schools are taught keyboarding beginning in kindergarten. Older students who never mastered handwriting say it doesn't affect their grades.
There are those who say the culture is at a crossing, turning from the written word to the typed one. If handwriting becomes a lost form of communication, does it matter?
It was at University of Virginia that researchers recently discovered a previously unknown poem by Robert, written in his unique script. Handwritten documents are more valuable to researchers, historians say, because their authenticity (真實(shí)性）can be confirmed. Students also find them more fascinating.
The loss of handwriting also may be a cognitive (認(rèn)知的）opportunity missed. Several academic studies have found that good handwriting skills at a young age can help children express their thoughts better-a lifelong benefit.
It doesn't take much to teach better handwriting skills. At some schools in Prince George's County, elementary school students use a program called Handwriting Without Tears for 15 minutes a day. They learn the correct formation of manuscript letters through second grade, and cursive letters in third grade.
There are always going to be some kids who struggle with handwriting because of their particular neurological (神經(jīng)系統(tǒng)的)wiring, learning issues or poor motor skills. Educators often point to this factor in support of keyboarding.
小題1:What is the author concerned about after 2011 SAT exams?
A．Keyboarding.B．Shorthand
C．Handwriting.D．Block letters.
小題2:A poem by Robert mentioned in the passage is used to _________.
A．prove how valuable handwriting is
B．explain what a famous poet he is
C．show how unique his poem is
D．stress how fascinating the documents are
小題3:The example of Handwriting Without Tears helps to argue that_________.
A．the schools are responsible for the loss of handwriting
B．the loss of handwriting is a cognitive opportunity missed
C．it doesn't take much to teach better handwriting skills
D．the culture is turning from the written word to the typed one
小題4: According to the author, when is a perfect time to learn handwriting?
A．Kindergarten.B．Primary school.C．High school.D．College.
小題5:What is the author’s attitude towards this debate?
A．Devotion.B．Encouragement.C．critical.D．Objective.

查看答案和解析>>

科目：高中英語 來源：不詳 題型：閱讀理解

When you travel in South America, you’d better pay attention to the following three kinds of dangerous South American animals.
Piranhas（水虎魚）
Although only a small number of piranhas are considered to be dangerous to humans, the red-bellied piranha is definitely one of those. Evidence has shown that a large group of piranhas can absolutely eat a herd of large animals crossing the river, leaving only bones. This fish lives in the freshwater streams of South America, and they can smell the blood from far away and launch attacks swiftly. It is said that they are only dangerous to humans if the water volumes are less and lower.
Anacondas（水蟒）
This South American monster of a creature often appears in the films or your nightmares！They have weighed over 230 kilograms. It is often considered to be the biggest snake in the world. You certainly don’t want to get caught alone with this snake due to its method of attacking and killing its victim. It is indeed a remarkably different brand of snake type as it regularly coils（纏繞）around all over its target, increasing the pressure until eventually its victim dies. Its jaws are powered by large muscles that produce enough power for its over 100 sharp teeth to pass through the thick skin of an crocodile. They don’t have poison. Sometimes they prefer to camouflage themselves so they look like their surroundings and swiftly draw back when humans are near.
Golden Poisonous Frogs
The golden poison frog might be the most-deadly of the South American animal, which is protected by means of poison. This very small frog, less than 55 mm in length, packs enough punch（效力）to take down a pair of African bull elephants. This apparently harmless frog has always been known to have killed people who have touched it directly. It’s also been noted that chicken and dogs have died by contacting things on which a golden poison frog had wandered! In intense colors, they normally look attractive to their targets.
小題1:What can we learn about piranhas from the passage?
A．Piranhas are the most dangerous animals.
B．Piranhas like to live in the deep seabed.
C．Piranhas may attack human beings when the water level is low.
D．Piranhas only attack human beings when they cross the river in groups.
小題2:How does an anaconda kill its victim according to the passage?
A．It often uses its poison to kill its victim.
B．It often uses its strength to kill its victim.
C．It kills its victim mainly using its powerful teeth.
D．It kills its victim with the help of other snakes.
小題3:The underlined word “camouflage” in Paragraph 3 means “________”.
A．hide itself by appearing like the surroundings
B．terrify and capture the enemy by making much noise
C．move around to search for delicious food
D．give off harmful gas to kill the targets
小題4:Chicken and dogs are mentioned in Paragraph 4 to show that ________.
A．no animals can survive the poison of the golden poison frog
B．they like to wander along the path of the golden poison frog
C．the golden poison frog likes eating them most
D．the poison of the golden poison frog is deadly

查看答案和解析>>

科目：高中英語 來源：不詳 題型：閱讀理解

Bicycle Safety

Operation　Always ride your bike in a safe, controlled manner on campus. Obey rules and regulations. Watch out for walkers and other bicyclists, and always use your lights in dark conditions.
Theft Prevention　Always securely lock your bicycle to a bicycle rack—even if you are only away for a minute. Register your bike with the University Department of Public Safety. It’s fast, easy, and free. Registration permanently records your serial number, which is useful in the possible recovery of the bike stolen.
Equipment
Brakes　Make sure that they are in good working order and adjusted properly.
Helmet　A necessity, make sure your helmet meets current safety standards and fits properly.
Lights　Always have a front headlight—visible at least 500 feet in front of the bike. A taillight is a good idea.
Rules of the Road
Riding on Campus　As a bicycle rider, you have a responsibility to ride only on streets and posted bicycle paths. Riding on sidewalks or other walkways can lead to a fine. The speed limit for bicycles on campus is 15 mph, unless otherwise posted. Always give the right of way to walkers. If you are involved in an accident, you are required to offer appropriate aid, call the Department of Public Safety and remain at the scene until the officer lets you go.
Bicycle Parking　
Only park in areas reserved for bikes. Trees, handrails, hallways, and sign posts are not for bicycle parking, and parking in such spots can result in a fine.
If Things Go Wrong
If you break the rules, you will be fined. Besides violating rules while riding bicycles on campus, you could be fined for:
×No bicycle registration…$25      ×Bicycle parking banned…$30
×Blocking path with bicycle…$40   ×Violation of bicycle equipment requirement…$35
小題1:Registration of your bicycle may help you 　　　.
A．find your stolen bicycleB．get your serial number
C．receive free repair servicesD．settle conflicts with walkers
小題2:According to the passage, what bike equipment is a free choice for bicycle riders?
A．Brakes.B．A helmet.C．A headlight.D．A taillight.
小題3:If you lock your bicycle to a tree on the campus, you could be fined 　　　.
A．$25B．$30C．$35D．$40
小題4: What is the passage mainly about?
A．A guide for safe bicycling on campus
B．Directions for bicycle tour on campus
C．Regulations of bicycle race on campus
D．Rules for riding motor vehicles on campus

查看答案和解析>>

科目：高中英語 來源：不詳 題型：閱讀理解

It had been a difficult move. I’d left my family and friends in Indiana, the beloved state where I’d lived most of my life. My new home in Florida was thousands of miles away from anything I knew. It was hot—all the time. Jobs were hard to come by, but I was up for almost any challenge.
At last, I taught in a special school where students have severe learning and behavioral difficulties.
Another teacher and I had spent weeks teaching the children appropriate behavior for public outings. Unexpectedly, only a few students, including Kyle, had not earned the privilege of going. He was determined to make his disappointment known.
In the corridor(走廊) between classrooms, he began screaming, cursing, spitting, and swinging at anything within striking distance. Once his outburst died down, he did what he’d done when he was angry at all his other schools, at home, even once at a juvenile detention(拘留)center. He ran.
People watched in disbelief as Kyle dashed straight into the heavy morning traffic in front of the school.
I heard someone shout, “Call the police!”
But I ran after him.
Kyle was at least a foot taller than me. And he was fast. His older brothers were track stars at the nearby high school. But I could run long distances without tiring. I would at least be able to keep him in my sight and know he was alive.
After several blocks of running directly into oncoming traffic, Kyle slowed his pace.
He took a sharp left. Standing next to a trash bin, Kyle bent over with his hands on his knees. I must have looked ridiculous. But his was not a look of fear. I saw his body relax. He did not attempt to run again. Kyle stood still and watched me approach. I had no idea what I was going to say or do, but I kept walking closer.
He opened his mouth to speak when a police car pulled up, abruptly filling the space between Kyle and me. The school principal and an officer got out. They spoke calmly to Kyle, who willingly climbed into the back of the vehicle. I couldn’t hear what was said, but I didn’t take my eyes off Kyle’s face, even as they drove away.
I couldn’t help but feel that I had failed him, that I should have done or said more, that I should have fixed the situation.
I shared my feelings with a speech therapist who was familiar with Kyle’s history. “No one ever ran after him before, Rachel,” she said. “No one. They just let him go.”
Things changed the day he ran and I ran after him, even though I didn’t have the right words, even though I wasn’t able to save him from the mess he was in. It was the day I didn’t throw my hands in the air and decide he was too fast, a waste of time and effort , a lost cause. It was the day my mere presence was enough to make a profound difference.
小題1:From the passage we know that _____.
A．the author left her family to Florida because jobs were hard to come by in Indiana.
B．students were allowed to go out after they passed some specific tests.
C．the author worked in a school where students were excellent.
D．no teacher had ever run after Kyle before except the author .
小題2:Which of the following description about Kyle is not true?
A．He had some behavioral difficulties and once moved from one detention to another.
B．He used to run out to let out his anger when he was in school,home or juvenile detention.
C．Different from his brothers, he learned in a special school while not a normal high school.
D．He was moved by his teacher who treated him with more patience and understanding.
小題3:Which is the correct order of the trace?
①He burst out when he knew he couldn’t go out.      ②I decided to run after him.
③Kyle stoppped beside a trash bin.                      ④A police car came and Kyle left with it.
⑤He rushed into the heavy morning traffic.       ⑥Kyle slowed his pace.
⑦I walked toward Kyle.
A．①⑤②⑥③⑦④B．①⑤②④⑥⑦③
C．⑤④②⑥③⑦①D．①②⑥⑦③④⑤
小題4:What is the best title of the passage?
A．Kyle, a Boy with Learning and Behavior Difficulties.
B．The Teacher Who Ran.
C．A School with Special Students.
D．A Terrible Conflict.

查看答案和解析>>

科目：高中英語 來源：不詳 題型：閱讀理解

This year’s Newsweek list of the top 100 high schools shows that today those with fewer students are rising.
Ten years ago, when the first Newsweek Top School List based on college-level test participation was published, only three of the top 100 schools had graduating classes smaller than 100 students. This year there are 22.
Fifty years ago, they were the latest thing in educational reform: big, modern high schools outside the cities with thousands of students. Big schools meant economic efficiency, a greater choice of courses, and better football teams. But only years later did we understand that it involved the difficulty of strengthening personal connections between teachers and students. SAT scores began dropping; on average, 30% of students did not complete high school in four years, a figure that rose to 50% in poor city neighborhoods. High schools for a variety of reasons seemed to have made little progress.
Size isn’t everything, but it does matter, and the past decade has seen a noticeable trend toward smaller schools. This has been partly due to the Bill and Melinda Gates Foundation, which has invested $1.8 billion in American high schools, helping to open about 1,000 small schools — most of them with about 400 kids, each with an average enrollment of only 150 students per grade. About 500 more are on the drawing board. Districts all over the country are taking notice, along with mayors in cities like New York, Chicago and San Diego. And most noticeable of all, there is the phenomenon of large urban and suburban high schools that have split up into smaller units of a few hundred.
Hillsdale High School in San Mateo, California, is one of those ranking No.423 — among the top 2% in the country. In 2003, Hillsdale remade itself into three “houses”. 300 students arriving ninth graders are randomly assigned to one of the houses, where they will keep the same four core subject teachers for two years before moving on to another for 11th and 12th grades. Teachers meet with students in groups of 25, five mornings a week, for open-ended discussions of everything from homework problems to bad Saturday-night dates. The advisers also meet with students privately and stay in touch with parents. Along with the new structure came the percentage of freshmen taking biology jumped from 17 to 95.”It was rough for some. But by senior year, two-thirds have moved up to physics,” says Jeff Gilbert. “Our kids are coming to school in part because they know there are adults here who know them and care for them.”
But not all schools show advances after downsizing, and it remains to be seen whether smaller schools will be a cure-all solution.
Ranking schools is always controversial. Over the years this system has been criticized for its simplicity — list of top U.S. high schools was made merely according to the proportion of students taking college-level exams. This year a group of 38 superintendents (地區(qū)教育主管) from five states wrote to ask that their schools should be excluded from the calculation. “It is impossible to know which high schools are ‘the best’ in the nation,” their letter read. “Determining whether different schools do or don’t offer a high quality of education requires a look at many different measures, including students’ overall academic accomplishments, their later performance in college, and taking into consideration the unique needs of their communities.”
小題1:What can we learn about the schools sponsored by the Bill and Melinda Gates Foundation?
A．They are often located in poor neighborhoods.
B．They are popular with high-achieving students.
C．They are mostly small in size.
D．Another 150 schools invested by the Foundation are planned to be set up.
小題2:According to Jeff Gilbert, the classes at Hillsdale were set up so that students could ______.
A．tell their teachers what they did on weekends
B．experience a great deal of pleasure in learning
C．maintain closer relationships with their teachers
D．deal with the demanding biology and physics courses
小題3:Newsweek ranks high schools according to ______.
A．their students’ academic achievement
B．the number of their students admitted to college
C．the size and number of their graduating classes
D．their college-level test participation
小題4:What attitude does the author have towards the present trend in high school education?
A．Subjective.B．Objective.C．Indifferent.D．Disapproving.
小題5:Which of the following can be the best title for the passage?
A．Providing Good Education for Baby Boomers
B．Top School List Winning National Support
C．Small Schools Rising in popularity
D．Students Meeting Higher Academic Standards

查看答案和解析>>

科目：高中英語 來源：不詳 題型：閱讀理解



If a diver surfaces too quickly, he may suffer the bends. Nitrogen (氮) dissolved (溶解) in his blood is suddenly liberated by the reduction of pressure. The consequence, if the bubbles (氣泡) accumulate in a joint, is sharp pain and a bent body—thus the name. If the bubbles form in his lungs or his brain, the consequence can be death.
Other air-breathing animals also suffer this decompression (減壓) sickness if they surface too fast: whales, for example. And so, long ago, did ichthyosaurs. That these ancient sea animals got the bends can be seen from their bones. If bubbles of nitrogen form inside the bone they can cut off its blood supply. This kills the cells in the bone, and consequently weakens it, sometimes to the point of collapse. Fossil (化石) bones that have caved in on themselves are thus a sign that the animal once had the bends.
Bruce Rothschild of the University of Kansas knew all this when he began a study of ichthyosaur bones to find out how widespread the problem was in the past. What he particularly wanted to investigate was how ichthyosaurs adapted to the problem of decompression over the 150 million years. To this end, he and his colleagues traveled the world’s natural-history museums, looking at hundreds of ichthyosaurs from the Triassic period and from the later Jurassic and Cretaceous periods.
When he started, he assumed that signs of the bends would be rarer in younger fossils, reflecting their gradual evolution of measures to deal with decompression. Instead, he was astonished to discover the opposite. More than 15% of Jurassic and Cretaceous ichthyosaurs had suffered the bends before they died, but not a single Triassic specimen (標(biāo)本) showed evidence of that sort of injury.
If ichthyosaurs did evolve an anti-decompression means, they clearly did so quickly—and, most strangely, they lost it afterwards. But that is not what Dr Rothschild thinks happened. He suspects it was evolution in other animals that caused the change.
Whales that suffer the bends often do so because they have surfaced to escape a predator (捕食動物) such as a large shark. One of the features of Jurassic oceans was an abundance of large sharks and crocodiles, both of which were fond of ichthyosaur lunches. Triassic oceans, by contrast, were mercifully shark- and crocodile-free. In the Triassic, then, ichthyosaurs were top of the food chain. In the Jurassic and Cretaceous, they were prey (獵物) as well as predator—and often had to make a speedy exit as a result.
小題1:Which of the following is a typical symptom of the bends?
A．A twisted body.
B．A gradual decrease in blood supply.
C．A sudden release of nitrogen in blood.
D．A drop in blood pressure.
小題2:The purpose of Rothschild’s study is to see ______.
A．how often ichthyosaurs caught the bends
B．how ichthyosaurs adapted to decompression
C．why ichthyosaurs bent their bodies
D．when ichthyosaurs broke their bones
小題3:Rothschild’s finding stated in Paragraph 4 ______.
A．confirmed his assumptionB．speeded up his research process
C．disagreed with his assumptionD．changed his research objectives
小題4:Rothschild might have concluded that ichthyosaurs ______.
A．failed to evolve an anti-decompression means
B．gradually developed measures against the bends
C．died out because of large sharks and crocodiles
D．evolved an anti-decompression means but soon lost it

查看答案和解析>>

同步練習(xí)冊答案