Little Tom down the street calls our dog "The keep dog". Zip is a sheep dog. But when Tom tries to say " Sheep", it comes out "keep". And in a way Tom is right. Zip is always bringing things home for us to keep! I'll tell you about some of them. Zip's first present was a shoe. It was made of green silk. We didn't know how Zip found the shoe. But after a moment, Mary, my big sister, told me the shoe had a strange smell. I nodded(点头) and held my nose. "What do you think it is?" "It smells like something for cleaning. I think someone tried to clean a spot (污点) off the shoe. Then he put it at the door to dry." Along came Zip. And good-bye shoe!" I said. "We should take it back." "We can't".said my sister. "Maybe little Tom is right," Mary said. "Maybe Zip is a keep dog!"

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    Elephants are able to know the difference between a man and a woman, and can tell an adult (成年人) from a child—all from the sound of a human voice. 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. Usually Masai people hunt elephants, and this suggests that animals have grown to listen for and avoid them.

    Prof. Karen McComb and Dr Graeme Shannon from the University of Sussex led the study. They explained that in former research they had used similar experiments to show that elephants could tell—from the sound of a lion—whether the animal was a female (雌性) or a more dangerous male (雄性).

    Prof. McComb wanted to find out if the animals used their very sharp sense of hearing to recognize danger from humans.

    The scientists recorded Masai men, women and children saying, in their own language, “Look, look over there, a group of elephants are coming.” They also recorded Kamba men saying this phrase.

    Masai people often come across elephants, which can result in violent (暴力的) hunting. Kamba people, however, mainly feed on agriculture, which does not generally bring them into violent touch with the animals.

    When the team played recordings of these different voices through a hidden speaker, they found that elephant family groups showed more fear in response to the voice of a Masai man, than to a Kamba man's voice. And the adult male Masai voices caused far more violent response than the voices of women or boys.

    The organic food has gained a lot of [popularity as they are being considered as healthier and tastier.  A fair number of people advocate a large-scale shift to organic farming from conventional agriculture. But this might not seem well-founded.

    Since the mid-19^th century, conventional industrial agriculture has become incredibly efficient on a simple land to food basis. Conventional farming gets more and more crop per square foot of land, which can mean less wilderness needs to be transformed to farmland.

    To make farming more efficient, conventional agriculture uses a significant amount of synthetic fertilizer（合成肥料）each year, and all that nitrogen（氮）enables much faster plant growth. However, the cost is paid in vast polluted dead zones at the months of many of the world's rivers, because much of the nitrogen ends up running off the soil and into the oceans. This also makes conventional farming one of the major threats to the environment.

To weaken the environmental impact of agriculture, improve soil quality as well as produce healthier foods, some farmers have turned to organic farming. Environmentalists have also welcomed organic food as better for the planet than the food produced by agricultural corporations. Organic practices — refusing artificial fertilizers and chemical pesticides –are considered far more sustainable. Sales of organic food rose 7.7% in 2010, up to $26.7 billion—and people are making those purchases for their moral senses as much as their tongues.

    Yet a new meta-analysis in Nature does the math and comes to a hard conclusion: organic farming produces 25% fewer crops on average than conventional agriculture.

    In the Nature analysis, scientists performed an analysis of 66 studies comparing conventional and organic methods across 34 different crop species, from fruits to grains. They found that organic farming delivered a lower output for every crop type, though the difference varied widely. For crops like fruit trees, organic trailed（落后于）conventional agriculture by just 5%. Yet for major grain crops and vegetables – all of which provide the world's main calories – conventional agriculture outperformed organics by more than 25%.

    What that means is that while organic farming may be more sustainable than conventional agriculture, there are trade-offs（此消彼长）with each. So an ideal global agriculture system may borrow the best from both systems rather than upholding merely organic or conventional practices.

    It may not come as a surprise but the world as a whole is getting richer. Some people have more disposable income to spend on luxuries such as holidays, cars, TVs and smartphones. Recent data has shown that the number of people living in extreme poverty has halved in recent decades. So should we celebrate the fact that more of us now have a better standard of living?

    Maybe not. While the gap between rich and poor in some countries is narrowing, there is still a lot of inequality in other places-some people have a lot of money and opportunities and others don't. A recent report by Oxfam and Credit Suisse revealed how divided many of us are when it comes to wealth. A lot of the money in the world is in the hands of very few people. In fact, 48% of global wealth is owned by the richest 1% of the population.

    But some countries are attempting to reduce this inequality and make the poor less poor. According to David Bryer from Oxfam, Brazil has been taking “some really sensible measures-measures around having more progressive tax, around investing in a higher minimum wage and investing in central public services.” Having a higher minimum wage(提高最低工资标准), can help people eat better and seek a better education. And more people with more money buy more things-and factories can produce more. In turn, a factory which produces more will need more workers. So, more jobs are created.

    Other wealthy individuals are doing their bit to help reduce inequality. Bill Gates, the founder of Microsoft, earned a lot of money from his company but when he retired, he and his wife Melinda, created a foundation to help the poor. He thinks that rich people should, of course, pay their taxes but he also advises that they should all “look at taking their wealth and being philanthropic, both in their own country and to help the global poorest.”

    Bill Gates feels that giving money to help poor people is “fulfilling”. But if other super-rich people don't want to experience this fulfilment then, according to Oxfam, very soon the wealthiest 1% will soon own more money than the rest of the world's population. Do you think that is fair?

    Our eating habits are very important for good health and a strong body. There are times when most of us would rather eat sweets and ice-cream than meat and rice. Sweets and ice-cream are not bad if we eat them at the end of a meal. If we eat them before a meal, they may take away our appetite（食欲）. It is important for us to eat our meals at the same time each day. When we feel hungry, it is a sign that our body needs food. When we feel angry or excited, we may not want to eat. A long time ago, in England, some judges used to decide whether a man was telling the truth by giving him some dry bread. If the man could not eat the bread, it showed that he was telling lies. Although this seems very strange and rather foolish, it is indeed a very good way of finding out the fact. A man who is worrying about something has difficulty in eating anything dry. Because he is worrying, he loses his appetite and does not want to eat.

    Dutch masters exhibition in Beijing

    The 17th century Dutch Golden Age had several significant artists and a range of great pieces produced during the period—including Jan Vermeer's Young Woman at Virginal, Jan Lievens' Boy in a Cape, and Turban and Rembrandt's Self-Portrait with Shaded Eyes.

    Some of the most refined examples of the time, including the three pieces mentioned above, will make their debut（首次亮相）in China as part of a world tour of The Leiden Collection.

    If you go:

9 a.m.-5 p.m., June 17-Sept 3 (closed on Mondays).National Museum of China, I Wusi Avenue, Dongcheng district. 010-6400-1476.

Ticket: 50 yuan ($7)

    The Age of Mechanical Reproduction

    The Age of Mechanical Reproduction, the latest exhibition at the Riverside Art Museum, features 41 artworks of US pop icon Andy Warhol, covering art installations, paintings and photographs. Warhol's well-known installation Electric Chair is a highlight of the show, which is also its debut in Asia.

    If you go:

10 a.m.-5 p.m., through August 28 (closed on Mondays).The Riverside Art Museum, Hongyan Road, Chaoyang district. 010-5309-2062.

Ticket: 60 yuan

Back with a bang

    Beijing-based hand Escape Plan will hold a concert in Beijing this weekend. The band is most famous for the song The Brightest Star in the Night Sky.

    If you go:

7:30 p.m., June 17.Beijing Worker's Gymnasium, Gongti Beilu, Chaoyang district. 400-610-3721.

Ticket: 280-980 yuan

Purple clay teapots

    Yixing purple clay potteries are a vital part of Chinese pottery culture and have been included in China's list of national intangible cultural heritage（国家非物质文化遗产）.A selection of more than 80 purple clay teapots will go on display at the Poly Art Museum starting Friday. The exhibit will include a range of delicate teapot works of Ji Yishun, Wang Xiaolong and Gao Lijun, who are all inheritors（继承人）the time-honored（历史悠久的）pottery handicraft.

If you go:

    9:30 a.m.-4:30 p.m.(closed on Sundays),through June 30.Poly Art Museum, New Poly Plaza,1 Chaoyangmen North Street 9.010-6500-8117.

Ticket: 20 yuan