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Big trees are very important in ecology. For a start, they provide food for countless other species and shelter for many animals. With their tall branches in the sun, they take in vast amounts of energy. This allows them to produce massive crops of fruit and flowers that much of the animal life in the forest feed on.
Only a small number of tree species have the genetic(基因的) ability to grow really big. The biggest are native to North America, but big trees grow all over the globe, from the tropics(热带地区) to the forests of the high latitudes(纬度). To achieve giant size, a tree needs three things: the right place to establish(建立) its seedling, good growing conditions and lots of time with low adult death rate. Lose any of these, and you will lose your biggest trees.
In some parts of the world, populations of big trees are dwindling because their seedlings cannot survive. In southern India, for instance, an aggressive non-native bush, Lantana camara, is invading the floor of many forests. Lantana grows so thickly that young trees often fail to take root. With no young trees to replace them, it is only a matter of time before most of the big trees disappear.
Without the right growing conditions, trees cannot get really big and there is some evidence to suggest tree growth could slow in a warmer world, particularly in environments that are already warm. Having worked for decades at La Selva Biological Station in Puerto Viejo de Sarapiqui, Costa Rica, David and Deborah Clark and colleagues have shown that tree growth there slows obviously in warmer years. “During the day, their growth shuts down when it gets too warm, and at night they consume more energy because their metabolic(新陈代谢的) rate increases,” explains David Clark. With less energy produced in warmer years and more being consumed just to survive, there is even less energy available for growth.
The Clarks’ theory, if correct, means tropical forests would be smaller over time. The largest, oldest trees would gradually die off and tend not to be replaced. According to the Clarks, this might cause a destabilization of the climate; as older trees die, forests would release some of their stored carbon into the atmosphere, causing a cycle of further warming, forest shrinkage and carbon emissions.
Besides, big trees face threats from elsewhere.
1.According to the passage, big trees make great contributions to the ecosystem because ________.
A. they can take in large amounts of energy
B. they determine the change of global climate
C. they provide the essentials for many creatures
D. they can improve a new cycle of further warming
2.All the following factors are a must for making big trees EXCEPT ______.
A. no deadly damage
B. the suitable place for new plants’ growing
C. good environment for growth
D. the highest location
3.The word “dwindling” (paragraph3) is closest in meaning to “______”.
A. exploding B. growing
C. changing D. dropping
4.What is the best title of the passage?
A. Big trees in trouble.
B. Advantages of big trees.
C. Results of big trees’ disappearing.
D. Importance of big trees to humans.
5.What will the author most probably discuss after the last paragraph?
A. More threats to the existence of big trees.
B. The effect of human activities on big trees.
C. Benefits of big trees to the whole atmosphere.
D. Comparison between common trees and big ones.
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Depression is the second most common cause of disability worldwide after back pain, according to a review of research. The disease must be treated as a global public health priority (优先考虑的事), experts report in the journal PLOS Medicine. The study compared depression with more than 200 other diseases and injuries as a cause of disability. “Globally, only a small part of patients have opportunities to be treated,” the World Health Organization (WHO) says.
Depression was ranked at number two as a global cause of disability, but its effects varied in different countries and regions. For example, rates of major depression were highest in Afghanistan and lowest in Japan. In the UK, depression was ranked number three in terms of years when people lived with a disability.
Dr Alize Ferrari from the University of Queensland’s School of Population Health led the study. “Depression is a big problem and we definitely need to pay more attention to it than we do now,” she told BBC News. “There’s still more work to be done in terms of awareness of the disease and also successful ways of treating it. The burden is different between countries, so the rate of depression tends to be higher in low and middle income countries and lower in high income countries.” Policy-makers have made an effort to bring depression to the forefront, but there is still a lot more work to be done.”
“There’re lots of confusions we know related to mental health,” Prof. Alize Ferrari explained. “What one person recognizes as disabling might be different to another person and might be different across countries as well, there are lots of cultural effects and explanations that are related to depression, which makes it more important to raise awareness of the size of the problem and also signs and how to find depression.”
The data—for the year 2010—follows similar studies in 1990 and 2000 looking at the global burden of depression. Commenting on the study, Dr Daniel Chisholm, a health economist at the department of mental health and substance abuse (药物滥用) at the WHO said depression was a very disabling condition.
“It's a big public health challenge and a big problem to be thought about but not enough is being done. Around the world only a tiny part of people get any sort of treatment or diagnosis.” Dr Daniel Chisholm said.
The WHO recently started a global mental health action plan to raise awareness of depression among policy-makers.
1. According to the passage, which of the following ranks NO. 1 among the causes of disability?
A. Cancer. B. Depression.
C. Back pain D. Heart disease.
2.What can we learn from the first paragraph?
A. Depression has been treated as a global public health priority.
B. PLOS Medicine is a website dealing with medical problems.
C. The study only analyzes depression all over the world.
D. Most patients with depression haven’t been treated.
3.Who is Alize Ferrari?
A. She is a doctor working in a hospital.
B. She is a professor at a university leading the study.
C. She is an official from the government.
D. She is a common teacher taking part in the study.
4.Which of the following is TRUE according to Paragraph 4?
A. There is a common standard of recognizing disability worldwide.
B. Most reasons for disability are similar.
C. Mental health has raised much attention among people.
D. How to find patients suffering from depression is not easy.
5.Why did the WHO start a global mental health action plan?
A. To make policy-makers of all countries pay attention to the problem of depression.
B. To help patients become healthier.
C. To raise the status of doctors in the world.
D. To help build more colleges that study mental health.
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High school graduation—the bittersweet feelings are as much a part of me now as they were twenty-one years ago.
As graduation day approached, excitement increased. Being out of high school meant I was finally coming of age. Soon I would be on my own, making my own decisions, doing what I wanted without someone looking over my shoulder and it meant going to school with boys—a welcome change coming from an all-girl high school. There was never any question in my mind that I would go to a college away from home. My mother’s idea, on the other hand, was just the opposite. Trying her best not to force her preferences on me, she would mildly ask whether I had considered particular schools—all of which happened to be located in or near my hometown of Chicago. Once it was established(建立) that, as long as the expenses would not be too heavy a burden on the family budget, I would be going away anyway, my family’s viewpoint changed. Their concern switched from whether I was going away to how far. The schools I was considering on the East Coast suddenly looked much more attractive than those in California. But which college I would attend was just one of what seemed like a never-ending list of unknowns: What would college be like? Would I be unbearably lonely not knowing anyone else who was going to the same school? Would the other students like me? Would I make friends easily? Would I miss my family so much that I wouldn’t be able to stand it? And what about the work—would I be able to keep up? (Being an A student in high school seemed to offer little hope I would be able to survive college.) What if the college I chose turned out to be a terrible mistake? Would I be able to switch to another school?
Then panic set in. My feelings took a 180-degree turn. I really didn’t want to leave high school at all, and it was questionable whether I wanted to grow up after all. It had been nice being respected as a senior by the underclass students for the past year; I didn’t enjoy the idea of being on the bottom rung of the ladder again.
Despite months of expectation, nothing could have prepared me for the impact of the actual day. As the familiar melody (旋律) of “Pomp and Circumstance” echoed in the background, I looked around at the other students in white caps and gowns as we seriously lined into the hall. Tears welled up uncontrollably in my eyes, and I was overcome by a rush of sadness. As if in a daze (恍惚), I rose from my seat when I heard my name called and slowly crossed the stage to receive my diploma(毕业文凭). As I reached out my hand, I knew that I was reaching not just for a piece of paper but for a brand-new life. Exciting as the future of a new life seemed, it wasn’t easy saying good-bye to the old one—the familiar faces, the familiar routine. I would even miss that chemistry class I wasn’t particularly fond of and the long travel each day between home and school that I hated. Good or bad, it was what I knew.
That September, I was fortunate to attend a wonderful university in Providence, Rhode Island. I needn’t have worried about liking it. My years there turned out to be some of the best years of my life. And as for friends, some of the friendships I formed there I still treasure today. Years later, financial difficulties forced my high school to close its doors forever. Although going back is impossible, it’s comforting to know I can revisit my special memories any time.
1. In this article the author mainly describes ________.
A. the great excitement before the graduation ceremony
B. her mixed feelings before graduation and on the actual graduation day
C. her happiness to be admitted to a wonderful university
D. her eagerness to go to a wonderful university far away from home
2. The author’s mother ________.
A. did not care very much which college her daughter went to
B. was greatly disappointed at her decision to go to a college on the East Coast
C. willingly allowed her to go to a college of her own choice
D. wished that she would study at a college or university close to home
3.Expectation and excitement suddenly changed into anxiety and fear. Which of the following did the author NOT mention as a reason for that change?
A. Growing homesick might seriously affect her physical health.
B. She might make a wrong choice and enter a university she did not like at all.
C. Her being a top student at high school did not mean she could be successful at college.
D. It might be hard for her to make friends in the new environment.
4.On the actual graduation day, ________.
A. she sang a song “Pomp and Circumstance”
B. she went through the whole ceremony in a daze
C. she came to realize that she was the only one who had a passion for her old school
D. reaching out for diploma, she was aware of a new stage in life ahead of her
5. The author adopts a(n)________ tone in writing this article.
A. negative B. serious
C. emotional D. cold-blooded
