An absolute description of the threat hanging over the world's mammals,reptiles,amphibians and other life forms has been published by the well-known scientific journal,Nature.A special analysis carried out by the journal indicates that an astonishing 41% of all amphibians on the planet now face extinction while 26% of mammal species and 13% of birds are similarly threatened.

    Many species are already critically endangered and close to extinction,including the Sumatran elephant,Amur leopard and mountain gorilla.But also in danger of vanishing（消失）for the wild,it now appears,are animals that are currently rated as merely being endangered.

    In each case,the finger of blame points directly at human activities.The continuing spread of agriculture is destroying millions of hectares of wild habitats every year,leaving animals without homes,while the introduction of newly-come species,often helped by humans,is also damaging native populations.At the same time,pollution and overfishing are destroying ocean ecosystems.

    "Habitat destruction,pollution or overfishing either kill off wild creatures and plants or leaves them badly weakened," said Derek Tittensor,an ocean ecologist at the World Conservation Monitoring Centre in Cambridge. "The trouble is that in coming decades,the additional threat of worsening climate change will become more and more common and could then kill off these survivors."

    The problem,according to Nature,is worsened because of the huge gaps in scientists knowledge about the planet's biodiversity.Evaluations of the total number of species of animals and plants alive vary from 2 million to 50 million.In addition,evaluations of current rates of species' disappearances vary from 500 to 36,000 a year. "That is the real problem we face," added Tittensor. "The scale of uncertainty is huge."

    In the end,however,the data indicate that the world is heading cruelly towards a mass extinction-which is defined as one involving a loss of 75% of species or more.This could arrive in less than a hundred years or could take a thousand,depending on extinction rates.

    Our risk of cancer rises dramatically as we age. So it makes sense that the elderly should be routinely screened for new tumors — or doesn't it?

    While such vigilant(警觉的) tracking of cancer is a good thing in general, researchers are increasingly questioning whether all of this testing is necessary for the elderly. With the percentage of people over age 65 expected to nearly double by 2050, it's important to weigh the health benefits of screening against the risks and costs of routine testing.

    In many cases, screening can lead to additional biopsies(活检) and surgeries to remove cancer, which can cause side effects, while the cancers themselves may be slow-growing and may not pose serious health problems in patients' remaining years. But the message that everyone must screen for cancer has become so ingrained(根深蒂固的) that when health care experts recommended that women under 50 and over 74 stop screening for breast cancer, it caused a riotous reaction among doctors, patients and advocacy groups.

    It's hard to uproot deeply held beliefs about cancer screening with scientific data. Certainly, there are people over age 75 who have had cancers detected by routine screening, and gained several extra years of life because of treatment. And clearly, people over age 75 who have other risk factors for cancer, such as a family history or prior personal experience with the disease, should continue to get screened regularly. But for the remainder, the risk of cancer, while increased at the end of life, must be balanced with other factors like remaining life expectancy(预期寿命).

    A recent study suggests that doctors start to make more objective decisions about who will truly benefit from screening—especially considering the explosion of the elderly that will soon swell our population.

    It's not an easy calculation to make, but one that make sense for the whole patient. Dr. Otis Brawley said, “Many doctors are ordering these tests purely to cover themselves. We need to think about the rational(合理的) use of health care and stop talking about the rationing of health care.”

    That means making some difficult decisions with elderly patients, and going against the misguided belief that when it comes to health care, more is always better.

    It's nearly exam time, so check out some of the best free apps(应用程序)around to help you manage the stress of exams and ensure you are studying effectively over the coming weeks.

Exam Countdown

    This app can help to remind you how many days, hours, and minutes you have until your exam. This can help to motivate you to hit the books before it's too late.

Block The Internet

    Are you constantly checking Facebook when you should be writing an essay? Or perhaps are you distracted by a battle in League of Legends? Download this app to get rid of online distractions by temporarily blocking Internet sites on your mobile. Simply add the websites you want to block and the period of time to block them for. Guarantee to get yourself focused on that assignment.

CBT-i Coach

    The US Department of Veterans (老兵)Affairs developed the app, CBT-i Coach, to assist with insomnia (失眠)and help people who would like to improve their sleeping habits. It provides several key parts: information about sleep and insomnia, strategies for improving sleep, relaxation skills and a helpful sleep diary.

Yoga(瑜伽)

    Yoga has great health benefits both for the mind and body and will help you to perform at your best while at university. Download a yoga app and have your own personal yoga instructor in your living room. You can choose from short or long workouts and have a qualified instructor teaching you how to do each pose(姿势). Choose from a variety of yoga routines and watch the instructional videos. Go on, stretch out those sore muscles.

    Young people can have problems with their minds. Some students become worried because they have to study very hard. Others have trouble getting on well with people like their parents and classmates.

    Li Wen, a junior 2student from No.2Middle School, could not understand his teacher and was doing badly in his lessons. He became so worried about it that he started to cut his finger with a knife. Another student16yearold Yang Fang from No.1Middle School, was afraid of exams. She got very worried in one and when she looked at the exam paper, she couldn't think of anything to write.

    A recent report from Jiefang Daily says about 18% of Shanghai teenagers have mental problems. Their troubles include being worried and very unhappy and having problems in learning and getting on with people. Many students who have problems won't go for advice or help. Some think they will look stupid if they go to see a doctor. Others don't want to talk about their secrets Liang Yuezhu, an expert on teenagers from Beijing Anding Hospital has the following advice for teenagers：

    Talk to your parents or teachers often.

    Take part in group activities and play sports.

    Go to see a doctor if you feel unhappy or unwell.

    Teens may become more private during adolescence (青春期) because they are learning how to be more independent, says Carl Pickhardt, a Texas­based scientist who studies parenting adolescents. "As they enter adolescence, parents have less control," he says. "You're going to have less communication with the kid who is now entering a larger and more risky world."

    However, Pickhardt says, this does not mean that parents should just sit back and do without any information. He says that parents should tell their kids that there are still things they need to know about, such as why their teen was late getting home from school one day.

    Iowa's mom Patty Link knows this fight well. The mom of three is raising two teenage boys: Graham, a 14-year-old eighth grader, and Carter, a 16-year-old high school student. She says that becoming friends with the parents of her children's friends has helped.

    "A lot of times if I want to get any information out of them, I'll say, 'Oh, I can talk to Adam's mom and she will tell me what was going on Friday night', and it will lead to some other discussion, "she says.

    Parents should watch their use of questions, Pickhardt says, because they can stand for authority (权威), and that is likely to not go over well with teens. "They want their independence to be respected, "he says. Pickhardt suggests using requests such as, "It could really help me if you could tell me," "I would really appreciate it if you let me know, "or "Could you help me better understand." But sometimes teens make mistakes and parents have to correct them. Parents should plainly (直率地) state the problem, Pickhardt says, and avoid judgments of character.

    Parents can also use technology to feel connected. One recent study showed that many teens are friends with their parents on Facebook—and only 5 percent limit what their parents can see.

It's well known that March 12th is China's annual National Tree Planting Day. On this day, people throughout China, will take spades and buckets (铲子和水桶) as well as young trees, and go out {#blank#}1{#/blank#}(green) their hometowns.

As a matter {#blank#}2{#/blank#}fact, China's Tree Planting Day could date back to a proposal {#blank#}3{#/blank#}(make) by Sun Yat-sen (孙中山) (1866—1925) and Qingming Festival (April 5th) was adopted (采纳) as Tree Planting Day then. However, April 5th was a late time for tree-planting in Southern China, so it was changed to March 12th in honour of Sun Yat-sen,{#blank#}4{#/blank#} passed away on March 12th.

In February 1979, the 5th National People's Congress of People's Republic of China {#blank#}5{#/blank#}(announce) that March 12th would be taken as Tree Planting Day, requiring the whole country to carry out tree planting {#blank#}6{#/blank#}(activity) on March 12th.

In recent years the tradition of tree-planting in the spring {#blank#}7{#/blank#}(observe) by Chinese people. For those living in the big cities, National Tree Planting Day is {#blank#}8{#/blank#}unique moment for city skipping.{#blank#}9{#/blank#} (apparent), it is convenient for people to have access to nature with their family members. After their fieldwork together, they get much {#blank#}10{#/blank#}(satisfy) from better environment. They also harvest closer family relations as well as enthusiasm for the future.