The African elephant, the largest land animal remaining on earth , is of great importance to African ecosystem(生态系统). Unlike other animals, the African elephant is to a great extent the builder of its environment. As a big plant-eater, it largely shapes the forest-and-savanna(大草原)surroundings in which it lives, therefore setting the terms of existence for millions of other animals that live in its habitat(栖息地).

    It is the elephant's great desire for food that makes it a disturber of the environment and an important builder of its habitat. In its continuous search for the 300 pounds of plants it must have every day, it kills small trees and underbushes, and pulls branches off big trees. This results in numerous open spaces in both deep tropical forests and in the woodlands that cover part of the African savannas. In these open spaces are numerous plants in various stages of growth that attract a variety of other plant-eaters.

    Take the rain forests for example. In their natural state, the spreading branches overhead shut out sunlight and prevent the growth of plants on the forest floor. By pulling down trees and eating plants, elephants make open spaces, allowing new plants to grow on the forest floor. In such situations, the forests become suitable for large hoofed plant-eaters to move around and for small plant-eaters to get their food as well.

    What worries scientists now is that the African elephant has become an endangered species. If the elephant disappears, scientists say, many other animals will also disappear from vast areas of forest and savanna, greatly changing and worsening the whole ecosystem.

    One fine afternoon I was walking along Fifth Avenue when I remembered that it was necessary to buy a pair of socks. I turned into the first sock shop that caught my eye, and a boy clerk who could not have been more than 17 years old came forward.

    “What can I do for you, sir?”

    “I wish to buy a pair of socks.”

    His eyes glowed. “Did you know that you had come into the best place in the world to buy socks?” I had not been aware of that.

    “Come with me,” said the boy happily. He began to haul (用力拖) down from the shelves box after box.

    “Hold on, boy, I am going to buy only one pair!”

    “I know that,” said he, “but I want you to see how beautiful these are. Aren't they wonderful?” There was on his face an expression of joy, as if he were showing to me the mysteries of his religion.

    “My friend,” said I, “if this is not just the enthusiasm (热情) that comes from novelty (新鲜), if you can keep up this day after day, in ten years you will own every sock in the United States.”

    In many shops the customer has to wait for someone to serve him. And when finally some clerk does notice you, you are made to feel as if you were disturbing him. He displays no interest either in you or in the goods he is paid to sell.

    Yet possibly that very clerk who is now so cold began his career with enthusiasm. As time goes by, the enthusiasm is gradually gone; his only pleasures were found outside of working hours. He became a mechanical (机械的), not inspired, salesman.

    I have observed such change in the lives of so many people in so many occupations that I have come to the conclusion that the fastest road to failure is to do things mechanically.

    Soaping up your hands may do more than just get rid of germs. It may wash away the inner confusion you feel right after being forced to make a choice between two appealing choices, according to a new study. The study builds on past research into a phenomenon known as “the Macbeth effect”.

    It turns out that Shakespeare was really onto something when he imagined lady Macbeth trying to clean her conscience（良心）by rubbing invisible bloodstains from her hands. A few years ago, scientists asked people to describe a past wrong act. If people were then given a chance to clean their hands, they later expressed less guilt than people who hadn't cleaned.

    This finding fascinated W. S. Lee, a researcher. “Anything from the past, any kind of negative emotional experiences, might be washed away,” says Lee.

He decided to test hand washing's effect on one kind of bad feeling: the tension we feel after being forced to choose between two attractive choices, because picking one choice makes us feel that we've lose the other. People usually try to calm this inner conflict by later exaggerating（夸大）the positive aspects of their choice.

    He had students rank 10 different music CDs. Then be offered students one CD as a gift. Some students then use liquid soap. Others only looked at the soap or sniffed（噢）it. “Actually, you do not need water and soap,” says Lee.

    Later, the students again had to rank all the music. People who didn't wash their hands had the normal response — they scored their take-home CD higher. Suggesting that they now saw it as even more attractive than before. But this wasn't true for the hand washers. They ranked the music about the same. “they feel no need at all to justify the choice,” say Lee.

    But the implications of it just aren't clear. Schwarz says it's too soon to know whether people should head for a sink after making a tough choice. He says washing may help decision-makers by cleaning away mental disorder, but perhaps if they don't go through the usual post-decision process of justifying their choice, they might feel more sorrow in the long run.

    When it comes to the most famous 20^th century painters of the United States, Grandma Moses should be mentioned, although she did not start painting until she was in her late seventies. As she once said to herself:" I would never sit back in a rocking chair, waiting for someone to help me." No one could have had a more active old age.

    She was born on a farm in New York State, one of five boys and five girls. At 12 she left home and was in domestic service until at 27 she married Thomas Moses, the hired hand of one of her employers. They farmed most of their lives, first in Virginia and then in New York State, at Eagle Bridge. She had ten children, of whom five survived; her husband died in 1927.

    Grandma Moses painted a little as a child and made embroidery(刺绣) pictures as a hobby, but only changed to oils in old age because her hands became too stiff(僵硬的) to sew and she still wanted to keep busy and pass the time. Her pictures were first sold at the local drugstore and at a market and were soon noticed by a businessman who bought all that she painted. Three of the pictures were exhibited(展览) in the Museum of Modern Art, and in 1940 she had her first exhibition in New York. Between the 1930's and her death, she produced some 2,000 pictures: careful and lively portrayals of the country life she had known for so long, with a wonderful sense of color and form. "I think really hard till I think of something really pretty, and then I paint it" she said.

    The new president of Harvard University is the son of an Eastern European refugee and Auschwitz (奥斯威辛) survivor—Lawrence S. Bacow. His father worked full time while attending a state college in Detroit at night to earn his degree.

    Bacow, the former president of Tufts University, has taken over Harvard at a time when higher education is under attack for being financially out of reach to many Americans. But Bacow said his family's journey had reflected the power of college education to transform generations and the opportunities that have historically been available in the United States.

    "My parents came to this country with almost nothing," Bacow said. "I wouldn't be here if this country had not been open to people like my parents at that time. Nor would I if my father hadn't had the opportunity to get the college education."

    Bacow grew up in Pontiac, Michigan. His father's family fled anti-Jewish (反犹太的) violence in Minsk, then part of the Soviet Union, before the start of World War II and went to the United States. His mother arrived in Brooklyn at age 19, having survived Auschwitz concentration camp. She was the only Jew from her town to have survived the war. Yet Bacow, who is married with two sons, said that while growing up in Michigan, he had a happy childhood, entering science fairs as a child and building radios like his dad.

    Bacow has spent most of his professional career at MIT, Harvard and Tufts. He was a professor of environmental studies at MIT, and later a principal at the university. He led Tufts from 2001 to 2011. At Tufts, Bacow earned a reputation for shaking up a sleepy university that was being overshadowed by its peers in Boston. He is also credited with leading it through both 9/11 and the 2008 financial crisis.

    As the Tufts president, Bacow traveled around the country, reaching out to alumni (校友), and he urged his faculty and deans to do the same, in an effort to boost donations to finance Tufts' academic ambitions. He raised more than $20 million for faculty recruitment, attracting up-and-coming professors by offering junior faculty perks (福利), such as long academic leaves that they couldn't get elsewhere.

    Under Bacow's leadership, Tufts spent millions on labs and libraries. He also made addresses nationally about the need to make higher education more accessible and affordable to low-income students.

    From early times, man has been interested in art. People have often worked together to collect and save the world's art treasures.

    Fine art treasures from many countries are kept in an art museum called the Louvre (卢浮宫) in Paris, France. The works of art have been collected by the people of France over many centuries. It is the biggest art museum in the world.

    The Louvre has not always been a museum. The first building was a fort (堡垒). In 1190, it was the king's castle with high walls and a round tower. It had a moat (护城河) to keep out the enemies.

    Over the years, the number of buildings around the fort grew. By 1350, the fort was no longer needed and became a palace home for French kings and queens. During times of peace, new treasures were brought in. During days of war, many treasures were stolen, and the buildings were damaged.

    When Francis Ⅰ became King of France in 1515, he brought in many artists from many countries. One of the artists was Leonardo da Vinci from Italy. He worked in Paris. Da Vinci's Mona Lisa is the best-known painting in the museum today.

    In 1793, the Louvre became a public museum, just as it is now. It is a place where art treasures are kept for everyone to enjoy. Every year millions of people from all over the world come to the Louvre to see the master-pieces.