Back in the 1860s, a British scientist named Henry Walter Bates noticed something interesting in the animal world: a kind of butterfly, Common Mormon, can change the pattern on its wings so that it looks like another butterfly species, the Common Rose, which is poisonous for birds to eat.

    Bates argued that animals develop this ability to protect themselves from being eaten. This theory had been widely accepted by scientists. But one question remains: how do these animals manage to do that?

    After more than 150 years, scientists are finally able to answer that question-it is all down to a gene(基因) called “doublesex", according to a study published on March 6 in the journal Nature.

    In fact, scientists have long known that genes are responsible for this useful ability. But until the new study, scientists hadn't been able to find out which genes in particular were responsible.

    Scientists at the University of Chicago compared the genetic structures of the Common Mormons that changed their wing patterns with those of ones that did not. And all the results pointed to a single gene, “doublesex”.

    This was much to the scientists' surprise. They used to expect that something as complex as this would be controlled by many different genes. For example, one gene would control the color of the upper part of the wing, one would do so for the lower part.

    However, the “doublesex” gene doesn't quite do everything by itself. Instead, it acts like a switch-it “tells” other genes to change the wing patterns. Isn't that clever?

    Scientists believe that this special ability of the “doublesex” gene on Common Mormon was developed throughout the long history of evolution. “The harmless species gains an advantage by resembling something predators(捕食者) avoid,” Sean Carroll, a scientist told Nature. “it was obvious evidence for natural selection.”

    It was a hot day, and my brother Walt and I had decided that the only way to survive it would be to go swimming in a deep swimming hole across Mr. Blickez's Pasture（牧场）and through some woods.

    The only problem with our plan was that this pasture was guarded by a huge, mean Hereford bull（公牛）. Mr. Blickez had told us that Elsie was the meanest bull in the town, maybe even in the county, and we believed him. But the hotter it got, the more we thought there was something fishy about his words. For one thing, we remembered Mr. Blickez liked telling tall tales; for another, Elsie seemed like a strange name for a bull.

    Finally, I talked Mom into asking permission for us to walk through the pasture, but then another problem surfaced. Mom said she would talk to Mr. Blickez if we would take our cousin Joanie along with us. Joanie was almost two years older than me and a head taller. If her teasing ever got around my grade school, it would be all over for me. In fact, I still had a headache from a quarrel with her that morning. “I'm not going swimming with that silly girl cousin,” I told my mom.

    “Either Joanie goes with, or you stay home alone,” Mom said in her serious tone（语气）. I gave in and we set out. On your way across the pasture, Walt yelled suddenly. Elsie had approached him quietly and was licking（舔）his back. Joanie and I dove under the wire fence, but while I was on the ground I looked up and saw that Elsie wasn't a big mean bull after all. She was going to keep licking my brother's back as long as he stood still.

    We had many good days growing up and visiting our secret swimming hole guarded by the so-called “big mean bull”. And as it turned out, for a girl cousin, Joanie hasn't been too bad. She's been one of my best friends over the years.

    On a cool morning, Wilson Kasaine heads out along a dirt path in southern Kenya. His calmness makes it easy to forget that he's tracking one of the most dangerous animals in the world. Kasaine is tracking lions—especially one lion called Marti, who is the real-life Lion King of Selenkay Conservancy.

    Tracking lions on foot may sound like a death wish, but Kasaine has been doing it for most of his life. Born into a traditional Maasai family he quickly grew to understand the beauty and danger of wildlife. Living with big wild animals forces him to develop a good sense of where they have been and where they may be going. During his 12-kilometer walks to and from school, he learned how to tell the paw prints (爪印)of a lion from those of other animals.

    Growing up, Kasaine knew that improving his tracking abilities would help him avoid surprise meetings with dangerous animals. For many Maasai, tracking is mainly a matter of self-protection. But Kasaine is tracking lions to meet them and to protect them. He leads a small group of wide-eyed tourists over the red sandy path, searching for the lion that has left upon it his prints.

Each year, thousands of tourists crowd Kenya's national parks to try to have a look at the"big five”; elephants, rhinoceros, leopards, buffaloes and lions. The international draw of these animals matters a lot because the nation's economy is tied to the protection of its wildlife. If Kenya's wildlife disappears, so does its second-largest source of income.

    Wildlife protection efforts in Kenya meant marking off land exclusively(专门地)for animals. But it also meant that the people who had originally lived in the area were forced to leave their land and into smaller surrounding areas. They are also finding it increasingly hard to keep a traditional Maasai lifestyle. But people are glad that it really makes a difference to wildlife protection.

Letter One

Dear Editor,

    After I finish my homework, I often go online and chat with my friends. Sometimes I play computer games. But my parents hate to see me playing games on the computer. Maybe they have heard too much news about how QQ and computer games harm children. Once I went to a net bar(网吧) to play games after school. But after that I told my parents that I was playing basketball at school. I said so because I didn't want to make them unhappy. I feel bad about it. However, I need to rest for a while by playing computer games after studying for a long time. I really want my parents to understand that. Do foreign parents do the same to their children? Please help me.

Li Ping,

Beijing

Letter Two

Dear Li Ping,

    I don't think it's strange for parents to keep their children away from anything bad. Foreign parents will do the same as your parents! They may not let their children watch TV for too long a time, or like your parents, they don't want their children to play computer games.

    Talk to your parents and be honest to them, I think. Tell them what you are doing and why you are doing so to make them understand you. It's never good to do things behind your parents. They aren't fools as you think sometimes! Our parents seem to know what is the best for us.

Remember: to be honest is the best way.

Good luck,

Rebecca

Early or Later Day Care

    Many young parents are confused about whether their children should have early day care, and there have always been different views on this subject.

    The British psychoanalyst John Bowlby believes that separation from parents during the sensitive "attachment" period from birth to three may scar a child's personality and lead to psychological problems in later life. Some people have drawn the conclusion from Bowlby's work that children should not be subjected to day care before three because of the parental separation it causes, and many people do believe this.

    According to Bowlby, a great deal of psychological harm can occur when young children are separated from their parents. If they are left without touch for a while, they will have a higher stress level. Parents' influence on their children's well-being may never be greater than during the earliest years of life, when a child's brain is developing rapidly and when nearly all of her or his experiences are shaped by parents and the family environment.

    However, there are critics. Some anthropologists (人类学家) point out that the love affair between children and parents found in modern societies does not usually exist in traditional societies. There has been a long history of the fact that father and mother did not bring up their children alone. Plato, around 394 B.C., argued that a system of early child care would free women to participate in society. Results from Israeli and Dutch studies show that child-raising duties are more evenly distributed among a broader group of people.

    Besides, studies have reported that early day care has a neutral or slightly positive effect on children's development. They learn the benefits of being socially smart, understanding the concept of sharing and caring. They promote concentration skills, which is very important in their learning. There are games where children are taught basic language and mathematical skills through stories and everyday examples.

    Common sense tells us that early day care would not be so widespread if children had problems with it. But Bowlby's analysis raises the possibility that it has delayed effects. The possibility that such care might lead to more mental illness 15 or 20 years later can only be explored by the use of statistics. Whatever the long-term effects, parents sometimes find the immediate effects difficult to deal with. Children under three dislike leaving their parents and show unhappiness. At the age of three almost all children find it easy to go to the nursery. The matter, then, is far from being clearly known, though experience and available evidence indicate that early day care is reasonable for young children.

    The theatre in Shakespeare's time was much different than it is today. Authors wrote plays for the masses, especially those who couldn't read or write.

    The theatre changed a lot during Shakespeare's lifetime. The authorities didn't like it and didn't allow acting in the city itself: They thought it had a bad influence on people and kept them from going to church. Queen Elizabeth, on the other hand, loved acting and helped the theatre become popular.

    The theatre in Shakespeare's time was full of life. People did not sit all the time and it was not quiet during the performance. The audience could walk around, eat and drink during the play.

    Theaters were open arenas or playhouses that had room for up to three thousand people. There was almost no scenery because the dialogue was the most important part of the play. Colourful and well-designed costumes were very important and told the people about the status of a character. Women never performed in plays, 80 young boys played female characters. The performances took place in the afternoon because it was too dark at night.

    There was no stage crew as there is today. Actors had to do everything themselves-from making costumes to setting the stage. Plays were organized by acting companies. They performed about 6 different plays each week because they needed money to survive. They had almost no time to rehearse (排练).

    The companies in Shakespeare's time had a rank system. The company belonged to shareholders and managers. They were responsible for everything and got most of the money when the company was successful. Sometimes they even owned their own buildings. Actors worked for the managers and after some time became a permanent member of the company. Apprentices (学徒) were young boys and were allowed to act in unimportant role. They also played female characters in plays.