Trees often grow to appear strong, which might make it hard to believe that they're easily harmed on the Inside. But that is the case, according to a worldwide survey of more than 200 types of trees. Researchers studied the inner part of the trees and found that most don't have a built-in safety net that would allow them to survive a serious drought.
"I think this is a really big deal." ecologist David Breshears said. He says it and other studies "keep pointing to: ‘Whoa, our forests are really fragile."'
Studies like this one are particularly worrying about climate change. The average temperature of the planet is rising. Scientists predict that warming will cause changes in rainfall patterns. That could lead to longer, more severe droughts in many regions around the world. As a result, the trees that now grow there could face a serious threat.
When drought strikes, trees begin to fail in the xylem(木质部), special tissue made of many tiny, strawlike tubes. This tissue makes it possible for a tree to draw water from the ground and deliver it to the leaves. During times of drought, tiny air bubbles can develop in the tubes. Too many bubbles block the flow of water——and lead to certain death for the tree.
Brendan Choat, a plant physiologist, worked on the new study along with 23 other researchers. All together the scientists studied 226 tree species in 81 different sites around the world. Choat said that this study is the first to look at all forest types and find so many species living on the edge. Of the 226 different types of trees Choat and his colleagues studied, 70 percent lived close to the point where a serious drought would stop water transport. Trees that flower, such as maples and oaks, were more vulnerable than conifers (针叶树), which, including pines and firs have evergreen, needlelike leaves.
Plant ecologist Bettina Engelbrecht said that in the interest of conservation, scientists can't just concentrate on a few species. "We have to worry about them all."
1. The first paragraph implies that trees .| A．can live through a drought. |
| B．have the ability to protect themselves |
| C．are worth a great deal of money |
| D．are weak as a matter of fact |
| A．The drought. | B．The tube. | C．The water | D．The xylem. |
| A．One-sided. | B．Fruitless. | C．Time-consuming. | D．Meaningful. |
| A．Care about the trees that flower. |
| B．Pay attention to all species of trees. |
| C．Find out why pines and firs are strong. |
| D．Study the trees living on the edge of death. |
| A．Serious drought is a threat to most trees |
| B．Trees face death due to lack of protection |
| C．Global warming reduces the number of trees |
| D．Trees reflect the change of the global climate |
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This is according to a study in which researchers played voice recordings to wild African elephants.
The animals showed more fear when they heard the voices of adult Masai men.
Livestock-herding Masai people do come into conflict with elephants, and this suggests that animals have adapted to specifically listen for and avoid them.
The study is published in Proceedings of the National Academy of Sciences.
Prof Karen McComb and Dr Graeme Shannon from the University of Sussex led the study. They explained that in previous research they had used similar playback experiments to show that elephants could tell --- from the sound of a lion’s roar --- whether the animal was a female or a more dangerous male.
Prof McComb wanted to find out if the animals used their very sharp sense of hearing to identify a potential danger from humans.
The scientists recorded Masai men, women and children saying, in their own language, “Look, look over there, a group of elephants is coming”.
They also recorded Kamba men saying this phrase.
While cattle-herding Masai people often come across free-ranging elephants, which can result in violent conflict, the Kamba people’s more agricultural lifestyle does not generally bring them into aggressive touch with the animals.
When the team played recordings of these different voices through a hidden loudspeaker, they found that elephant family groups reacted more fearfully in response to the voice of a Masai man, than to a Kamba man’s voice.
And the adult male Masai voices encouraged far more of these defensive reactions than the voices of women or boys.
1. An elephant can tell a man from a woman by sense of ________.
| A．touch | B．sight | C．smell | D．hearing |
| A．By observing the elephants in the zoo. |
| B．By playing voice recordings to them. |
| C．By recording the behaviours of elephants. |
| D．By communicating with them in a special way. |
| A．Masai men | B．Masai women |
| C．Kamba men | D．Kamba women |
| A．Elephants and human beings |
| B．Differences between human voices |
| C．Elephants recognise human voices |
| D．Elephants conflict with human beings |
【推荐2】Adopting (领养) a new pet should be an exciting and rewarding experience. But just as all families are different, so are all pets. Learn what to consider before you find your new furry family member.
All pets require their owner’s time, so Theisen, an expert in pet care, says how much time you can give to the pet is the top thing to consider. “If you adopt a 4-year-old cat, she’s not going to need the same amount of care as a 9-week-old dog”. says Theisen.
Like dating and finding the perfect partner, you want a pet that shares your interests and activity levels, particularly if you’re looking for dogs. “Consider activity levels in the family,” says Theisen. “If you’re a couch potato, or in other words, a homebody, look for a pet that matches that activity level.”
Some dogs, like Dalmatians and Terriers, can be loud and noisy and demand a more active lifestyle and room to be outside; they might not fit as well in close living situations as more sedentary pets. The Humane Society of the United States encourages potential owners to research books and websites and talk to other pet owners when considering adopting a new pet.
Theisen says that potential owners should go beyond the first impression of loveliness and watch how the animals interact with them. “There are dogs that will jump to the gate to meet you,” says Theisen. “And there are dogs that sit there with their sad doggy eyes — you know they’re not going to be high-energy dogs”.
Some exotic pets, like tortoises and parrots, are likely to live longer than dogs and cats — and even their human owners. They can also grow to be much larger than they were when they first came to live with their owners. Owners should make sure that their living situations should be continually updated and also prepare for the animal’s future.
1. What will people have to consider first of all when they plan to adopt a pet?| A．The amount of time they can give to the pet. |
| B．The money that the pet will cost them. |
| C．Whether the pet is lovely or not. |
| D．Whether the pet is active or not. |
| A．weak. | B．noisy. |
| C．loud. | D．inactive. |
| A．Dalmatians. | B．Terriers. |
| C．Parrots. | D．Bulldogs. |
| A．A guidebook. | B．A fashion magazine. |
| C．A Life magazine. | D．An entertainment newspaper. |
【推荐3】By four months of age, the cognitive performance of ravens in experimental tasks testing their social intelligence and understanding of the physical world parallels that of adult great apes according to a new study.
Previous studies have demonstrated impressive cognitive abilities in ravens. These birds are capable of considering the visual perspective of others, planning for the future, and insightful problem-solving. Ravens have even been called “feathered apes”. But can they really compare with, primates when it comes to higher cognition?
To put this question to the teal, Pika and colleagues adapted a battery of experimental tests designed for primates to meet the needs or ravens. They include both physical and social cognitive skills. Physical cognitive skills include special memory, understanding relative numbers and addition, and causal reasoning, while social cognitive skills include social learning, communication, and theory of mind.
Pika and colleagues conducted their tests with eight hand-raised ravens. The researchers found that, at four months old, ravens already possessed a full-blown set of cognitive skills and did not significantly change over the time period investigated.
Comparing the performance of the ravens with chimpanzees, Pika and colleagues found that, with the exception of special memory, the ravens' performance equalled that of the great apes. The findings strengthen the idea that ravens, like great apes, have evolved general, flexible cognitive skills, rather than being highly specialized in a few ones only.
However, the researchers caution that the performance of these eight ravens may not be representative of the species as a whole. The birds in this study were tested by two highly familiar people who had hand-raised them. Such socialization factors could affect how the birds perform in cognitive tests designed and administered by humans.
1. Ravens have been called “feathered apes” for their________.| A．vision | B．speed | C．strength | D．intelligence |
| A．Ravens' development lops out at four months. | B．Primates couldn't perform as well in the tests. |
| C．Pika laid emphasis on physical cognitive skills. | D．Ravens develop comprehensive cognitive skills. |
| A．Limitations of the study. | B．Conclusion of the study. |
| C．Significance of the study. | D．Expectation of the study. |
| A．The Raven: A Birdbrain Nevermore | B．The Raven: A Mystery to Be Solved |
| C．The Raven: A Superstar in Experiment | D．The Raven: A Representative of the Species |
【推荐1】The Truth about Your Memory
What would you be without your memories? How important is your ability to remember the past and to draw on it to help you know what to do next? I’ll answer tor you: It’s right up there with breathing and eating.
However, most people know little about memory. A study by research psychologists Daniel Simons and Christopher Chabris asked people simple questions about memory and then compared their answers with those of experts in memory research.
So how does memory work?
In other words, there is no consistent or orderly sense to memory. A memory will be hidden away and connected to other memories or concepts in ways that are not necessarily practical or logical.
| A．The researchers had a very tough time understanding human memories. |
| B．The human brain is still a mysterious universe in many ways, of course. |
| C．A research shows recalling the past can change the memory of what really happened. |
| D．The results show how far removed from reality the public's beliefs about memory are. |
| E．One would think that understanding how memory works would be a high priority for all people. |
| F．I prefer to describe it as something like an old man sitting by a campfire somewhere deep in your brain. |
| G．This is why a particular smell or sound may bring up a memory even though it wasn’t important in the original experience. |
Some historians believe that he is based on a real person, Samuel Wilson. During the War of 1812, Wilson sold meat to American troops. Wilson labeled the meat barrels (桶) US. This meant that it was for the army. At that time, US was not used to mean “United States”. An officer asked what the US on the barrels meant. A soldier replied, “United States”, meaning Samuel Wilson.
The Uncle Sam image (形象) today shows a man with a beard, a stars and stripes (星条旗) top hat, and a suit. Thomas Nast created this image in about 1838. It represented the government in Nast’s political cartoons. Some people believe that Nast based his image on Dan Rice, a popular entertainer. Rice performed while wearing a top hat and suit.
Others think it was James M. Flagg that drew the most famous image of Uncle Sam in 1917, during World War I. It shows a serious man pointing a finger at the viewer and says “United States”. Flagg drew this enduring image to encourage Americans to join the U.S. Army. It has been used for this purpose ever since.
Today, Uncle Sam is a symbol of the United States that is recognized around the world.
1. Which of the following is TRUE according to the passage?
| A．Uncle Sam was a character created by the government of the United States. |
| B．Samuel Wilson, a businessman, sold meat to American troops during the War of 1812. |
| C．Uncle Sam was based on an entertainer to show Americans were popular people. |
| D．The image of Uncle Sam has been used to urge Americans to join the army since 1838. |
| A．long-lasting | B．short-lived |
| C．painful | D．scary |
| A．Uncle Sam is an officer from the American army |
| B．Uncle Sam’s top hat and suit reflect the American flag |
| C．Tile Uncle Sam symbol is the best of all American symbols |
| D．Opinions differ about how Uncle Sam became a national symbol |
| A．The name Uncle Sam was invented during the War of 1821. |
| B．There are many symbols of the United States, including Uncle Sam. |
| C．Over time, the image of Uncle Sam came to represent the United States. |
| D．Uncle Sam is a national symbol that is recognized around the United States. |
Farmers can do call on the services of their local hunt to control the fox population . Hunting consists of hunting a fox across the countryside, with a group of specially trained dogs, followed by men and women riding horses. When the dogs eventually catch the fox , they kill it or a hunter shoots it.
People who take part in hunting think of it as a sport ; they wear a special uniform of red coats and white trousers , and follow strict codes of behavior. But owning a horse and hunting regularly is expensive, so most hunters are wealthy.
It is estimated (估计) that up to 100,000 people watch or take part in fox hunting . But over the last couple of decades the number of people against fox hunting , because they think it is cruel, has risen sharply. Nowadays it is rare for a hunt to succeed without some kind of
Noisy confrontations between hunters and saboteurs have become so common that they are almost as much a part of hunting as the hunting of foxes itself. But this year supporters of fox hunting face a much bigger threat to their sport. A Labour Party Member of the Parliament, Mike Foster, is trying to get Parliament to pass a new law which will make the hunting of wild animals with dogs illegal. If the law is passed, wild animals like foxes will be protected under the ban in Britain.
1. What is special about fox hunting in Britain?
| A．It involves the use of a deadly poison. |
| B．It is a costly event which rarely happens. |
| C．The hunters have set rules to follow. |
| D．The hunters have to go through strict training. |
| A．keep farmers from hunting foxes. |
| B．forbid hunting foxes with dogs. |
| C．stop hunting wild animals in the countryside |
| D．prevent fox hunting in large numbers |
| A．reunion(联合) | B．conversation(对话) |
| C．conflict(冲突) | D．relationship |
Now a mother-daughter team in Ahmedabad, India has come up with a clever way to get drivers to pay more attention－a 3-D zebra crossing with an optical illusion (视错觉).
Artists Saumya Pandya Thakkar and Shakuntala Pandya were asked to paint the crosswalks by IL&FS, an Indian company that manages the highways in Ahmedabad. The corporation was looking for a creative solution to help the city’s residents to cross the busy accident-prone (易出事故的) roads safely. Thakkar and Pandya, who had previously seen images of 3-D zebra crossings that gave drivers the illusion of logs(原木)of wood on the streets in Taizhou, China, decided to test if a similar way would work in India.
Sure enough, in the six months that the 3-D crosswalks have been painted across four of the city’s most dangerous highways, there have been no accidents reported! The artists say that while it may appear that the zebra crossing could cause the drivers to brake suddenly and endanger the vehicles behind, such is not the case. Because of the way the human eye works, the illusion is only visible from a distance. As they get closer, the painting looks just like any other ordinary zebra crossing. The creators hope that their smart design will become increasingly common throughout India and perhaps even the world. So let’s look forward to it.
1. What can we learn from the first paragraph?
| A．Most drivers will slow down at zebra crossings. |
| B．Common zebra crossings don't function well. |
| C．Drivers have to stop when approaching zebra crossings. |
| D．About 95% of the drivers choose to speed up when approaching zebra crossings. |
| A．Because the drivers consider the safety of pedestrians. |
| B．Because the drivers don’t want to brake suddenly and endanger the vehicles behind. |
| C．Because the drivers are afraid of being fined for breaking the traffic rules. |
| D．Because the drivers mistake them for logs of wood on the streets. |
| A．the theory of the 3-D zebra crossings. |
| B．the popularity of the 3-D zebra crossings. |
| C．the shortcoming of the 3-D zebra crossings. |
| D．the positive effect of the 3-D zebra crossings. |
| A．Approving | B．Doubtful | C．Cautious | D．Objective |
【推荐2】With a brain the size of a pinhead, insects perform fantastic navigational (导航的) abilities. They avoid obstacles and move through small openings. How do they do this, with their limited brain power? Understanding the inner workings of an insect’s brain can help us in our search towards energy-efficient computing, physicist Elisabetta Chicca of the University of Groningen demonstrates with her most recent result: A robot that acts like an insect.
In search of the neural (神经的) mechanism that drives insect behaviour, PhD student Thorben Schoepe developed a model of its neuronal activity and a small robot that uses this model to navigate. Schoepe’s model is based on one main principle: always steer towards the area with the least apparent motion.
He had his robot drive through a long “corridor”— consisting of two walls with a random print on it—and the robot centred in the middle of the corridor, as insects tend to do. In other virtual environments, such as a space with obstacles or small openings, Schoepe’s model also showed similar behaviour to insects.
“The model is so good,” Chicca concludes, “that once you set it up, it will perform in all kinds of environments. That’s the beauty of this result.”
The fact that a robot can navigate in a realistic environment is not new. Rather, the model gives insight into how insects do the job, and how they manage to do things so efficiently.
Chicca explains, “Much of robotics is not concerned with efficiency. We humans tend to learn new tasks as we grow up and within robotics. This is reflected in the current trend of machine learning. But insects are able to fly immediately from birth. An efficient way of doing that is hardwired in their brains. In a similar way, you could make computers more efficient.”
1. Why does Chicca want to study how the insect brain works?| A．To make computers more efficient. | B．To make use of insects’ brain power. |
| C．To understand the habit of insects. | D．To reveal the inner part of insects’ brain. |
| A．Stretch. | B．Stare. | C．Drive. | D．Work. |
| A．Regretful. | B．Shocked. | C．Confused. | D．Satisfied. |
| A．How to make a robot that acts like an insect. |
| B．Why insects navigate more efficiently than robots. |
| C．Why a robot can navigate in a realistic environment. |
| D．How humans tend to learn new tasks as they grow up. |
More and more American students are currently studying at German colleges. That number has increased 20% over the last three years. Living costs are about $7,000 a year, which is even lower than in other European countries. Germany encourages international students. They create a multicultural landscape that benefits German students as well. According to a new report, Germany is home to six of the world’s 100 best universities. These schools offer around 900 degrees completely in English and many German students speak the language.
You could be part of Finland’s excellent education system. The Finns charge no tuition and offer a number of courses purely in English. They would be happy for you to add flavor to their school scene. Cost of living there is high. Be prepared for frosty winters that far north, but you will get that sweet midnight sun in the summer.
Many other European nations offer cheap or free college for foreign students, but if South America is more your thing, try Brazil. Most of the education will take place in Portuguese, so if that is in your plan you can study near beautiful beaches and jungles. The University of Sao Paulo and State University of Campinas are both highly ranked internationally. Your money will go a long way there, too.
Many of the lessons you will learn will be outside the classroom. Living on the economy in a foreign country will keep you on your toes. You will learn new customs, how to bargain, stay safe, budget and become more flexible with people. There is no better way to learn a language than by immersing yourself in it. At first, it will be the toughest thing you have ever done. Eventually, it will become second nature.
1. German universities are popular among US students mainly because _________.
| A．they offer a multicultural landscape |
| B．they belong to the world’s best ones |
| C．the cost of living there is reasonable |
| D．the students can get their degrees easily |
| A．students can learn to earn some money after class |
| B．many universities are surrounded by beautiful sceneries |
| C．Brazil provides excellent education to foreign students |
| D．students needn’t worry about their expense in Brazil |
| A．Foreign students are welcomed in Finland. |
| B．Studying abroad wisely can reduce your expense. |
| C．Students can learn English well only by learning abroad. |
| D．Cost of living in Finland is high because of its special climate. |
| A．Critical. | B．Encouraging. |
| C．Doubtful. | D．Objective. |
【推荐1】In a grey office building of Helsinki a social worker is meeting six elderly people from around town for lunch- via tablets on heir kitchen table. For the next half-hour she talks to them about their day and reminds them to have something to drink, because dehydration is particularly dangerous for older people.
The virtual lunch group is part of Helsinki's remote-care program for its elderly. While many counties with large elderly populations are building new care homes. Finland is not planning to do so and, instead, is looking after people in their own homes for longer. The guiding principle in Finland is that for anyone, no matter what their age. “home is best”.
In Helsinki's home -care program about 4, 000 old people are equipped with various safety devices. These include wristbands with GPS, a fall detector and a phone line linked to care workers who monitor the wearer' s location on their computer screens. Most of the old people are too weak to walk about much, so they rarely leave their homes. But if they venture out in the middle of the night, care workers are to find them. Local tech companies have developed systems that use a network of motion sensors to gather data on things like how much a person moves about, visits the bathroom or opens the fridge. Not opening the fridge as much, for example, is a sign that memory problems may be getting worse.
Technology sometimes misfires. Wristbands give out the wrong location, setting off false alarms. A sensor may fail because Grandpa covers a towel over it. Some elderly people forget to charge their tablets. Such problems can be fixed. The biggest gain from technology may be that it makes it easier to keep old people fit enough to remain in their own homes for longer. This is much cheaper than an institution, and usually nicer, too.
1. What does the underlined word “dehydration” in paragraph 1 refer to?| A．Talking less. | B．Eating alone. |
| C．Watching their tablets. | D．Losing too much water. |
| A．To build more lunch groups. | B．To make the old stay at home. |
| C．To guide elderly people to care homes. | D．To care for the old in their own homes. |
| A．To find the missing old people. | B．To monitor the wearer’s location. |
| C．To collect the wearers' activity data. | D．To check people's memory problems. |
| A．Grandpa uses a towel. | B．The tablets are out of power. |
| C．Wristbands send out an alarm. | D．The elderly forget their location. |
【推荐2】Walk Through History
It’s no surprise to anyone who’s been to Charleston that it is among the best US cities to visit. “It can feel like you’re in a dream sometimes, like you’ve stepped back 200 years,” says Brian Sim ms, the owner of Charleston Sole Tours. These are Simms’s must-sees.
African-American Heritage Tour“People don’t realize how much African culture is here.” says Sim ms. He recommends learning about the African-American heritage that shaped the city, region and country to fully understand Charleston.
Gullah Tours offers a two-hour bus tour for $ 18.www.gullahtours.com
Battery and White Point GardensA large public park and garden with walking paths and artifacts —all shaded by beautiful trees.
Free admission. Simms provides two- hour guided tours for $10 to $20. www.charlestonsole.com
Middleton PlaceMiddleton Place is a historic plantation with vivid exhibits and a working table. It provides an all-around view of what was going on with the history of the families that ran the plantation.
$ 28 / adult; $ 15 / student 14 and older; $ 10 / child 6-13; free / under age 6. www.middleton place.org
Fort Summer National MonumentMarking the site where the first shots of the Civil War were fired, this historic place includes several sites around Charleston Harbor and an education center at Gadsden’s Wharf. The best time of year to visit is spring—when the azaleas are flowering—or fall.
Admission is free. Boat ride is $ 19.5 / adult, $ 12 / child. www.nps.gov/fosu
1. If you like walking under the shade of trees,which is the best place for you to go?| A．Fort Sumter National Monument | B．Middleton Place |
| C．Battery and White Point Gardens | D．African-American Heritage Tour |
| A．$71 | B．$81 | C．$56 | D．$91 |
| A．Spring is the only best season to visit Fort Sumter National Monument. |
| B．All the people must pay money if they want to visit Middleton Place. |
| C．You can learn American culture’s influence on Africa when visiting African-American Heritage Tour. |
| D．All the four tours don’t offer free admission. |
【推荐3】A latest study on people who eat red meat has found they have higher risks of heart disease and early death. The finding goes against other recent research that suggested removing meat from one's diet has few health benefits. The two opposing findings can make it difficult for people to make sense of what can seem to be conflicting messages on food.
Duane Mellor, a dietician at Aston University, and other researchers say that after examining research on the subject, moderation may be the best way forward. “In this case, eating a certain amount of meat, including red meat, is likely to be safe,” Mellor said. “However, in the interest of health, reducing meat intake to the recommended less than 70 grams per day would be sensible.”
A researcher with ties to the meat industry published a report on the subject in 2019, saying that people should not reduce the amount of red meat they eat. Some experts criticized the findings because they were in conflict with dietary advice from international agencies.
The latest study found that eating two servings a week of red meat or processed meat was linked to a 3% to 7% higher risk of heart disease and also a 3% higher risk of all causes of death. Norrina Allen, a co-leader of the latest study, said the health risk is small but people should try to change their diet. “It's a small difference, but it's worth trying to reduce red meat and processed meat.” She added that eating red meat is also regularly “linked to other health problems like cancer.”
The World Cancer Research Fund says red and processed meat may cause cancer. It recommends eating red meat with an upper limit of 500 grams cooked weight per week-and “little, if any” processed meat. They said on average, adults should reduce the amount of meat they eat by 50% and they should eat twice as much nuts, fruits, vegetables and beans.
1. What does the latest study suggest?| A．People should not cut down on the amount of red meat they eat. |
| B．People should remove meat from their diet for the benefit of health. |
| C．Eating red meat is linked to higher risks of heart disease and early death. |
| D．Eating two servings a week of red meat or processed meat has no health risks. |
| A．Doing research by oneself. |
| B．Following one's own heart. |
| C．Avoiding conflicts with others. |
| D．Staying within reasonable limits. |
| A．It will help improve our eating habit. |
| B．It is in conflict with her former study. |
| C．It has offered two regular cures for cancer. |
| D．It makes no difference to the meat industry. |
| A．Some tips on cooking. |
| B．Advice on a healthy diet. |
| C．Research on the cause of cancer. |
| D．Ties between meat and vegetables. |
