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Monarch without a KingdomThis November, a hundred million butterflies will drop from the sky over Mexico, like autumn leaves. But for how long Genetically modified maize (玉米) could mean extinction for this beautiful butterfly, Rafael Ruiz reports.Although its body is about 3 cm long and it only weighs 1 gm, the Monarch butterfly manages to travel 5,000 km each year. It seems to be so fragile, but its long journeys are proof of its amazing ability to survive. This autumn, the Monarch butterfly will once more set out on its journey from the U.S. It will keep going until it reaches Mexico. It travels these huge distances to escape the cold weather in the north.In November, millions of Monarchs fall like bright, golden rain onto the forests in the mountains of central Mexico. In the silence of these mountains you can hear a strange flapping (拍动) of wings, as the Monarchs arrive at their destination. In the mountains, which reach a height of 3,000 meters, the butterflies are safe.Before reaching their journey"s end they have faced strong winds, rain and snowstorms and they do not all manage to reach their destination. When the winters are really bad, perhaps 70 per cent of them will not survive. Their long journey to Mexico is thought to be one of the most amazing events in the whole of the American continent. When they get there they will stay until the beginning of April, when their internal calendar tells them that it is time to go back. The long journey, with all its dangers, begins again.These delicate creatures now face danger of another kind—from scientific progress. In the U.S., millions of farms grow genetically modified maize which is pure poison for the butterfly. Laboratory experiments have shown that half of the butterflies which feed on the leaves of genetically modified maize die within 48 hours. Not all experts agree that this variety of maize is responsible for the threat to the Monarchs. In spite of these doubts, the European Union has refused to approve new crops of genetically modified maize until further investigations have been carried out.Greenpeace is campaigning against genetically modified products (in Spain, there are already 20,000 hectares of modified maize). The environmental organization recently published a list of 100 species of butterfly in Europe alone which are threatened with extinction. The Monarch butterfly looks fragile.
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"Salty" Rice Plant Boosts HarvestsBritish scientists are breeding a new generation of rice plants that will be able to grow in soil containing salt water. Their work may enable abandoned farms to become productive once more.Tim Flowers and Tony Yeo, from Sussex University"s School of Biological Sciences, have spent several years researching how crops, such as rice, could he made to grow in water that has become salty.The pair has recently begun a three-year programme, funded by the Biotechnology and Biological Sciences Research Council, to establish which genes enable some plants to survive salty conditions. The aim is to breed this capability into crops, starting with rice.It is estimated that each year more than 10 million hectares (公顷) of agricultural land are lost because salt gets into the soil and stunts (妨碍生长) plants. The problem is caused by several factors. In the tropics, mangroves (红树林) that create swamps (沼泽) and traditionally formed barriers to sea water have been cut down. In the Mediterranean, a series of droughts have caused the water table to drop, allowing sea water to seep (渗透) in. In Latin America, irrigation often causes problems when water is evaporated (蒸发) by the heat, leaving salt deposits behind.Excess salt then enters the plants and prevents them functioning normally. Heavy concentrations of minerals in the plants stop them drawing up the water they need to survive.To overcome these problems, Flowers and Yeo decided to breed rice plants that take in very little salt and store what they do absorb in cells that do notaffectthe plants" growth. They have started to breed these characteristics into a new rice crop, but it will take about eight harvests before the resulting seeds are ready to be considered for commercial use.Once the characteristics for surviving salty soil are known, Flowers and Yeo will try to breed the appropriate genes into all manners of drops and plants. Land that has been abandoned to nature will then be able to bloom again, providing much needed food in the poorer countries of the world. Which of the following statements about Flowers and Yeo is true
Global warming would have a devastating impact on low, lying island.
Houses in 18th Century North AmericaSeventeenth-century houses in colonial North America were simple structures that were primarily functional, carrying over traditional designs that went back to the Middle Ages. During the first half of the eighteenth century, however, houses began to show a new elegance. As wealth increased, more and more colonists built fine houses.Since architecture was not yet a specialized profession in the colonies, the design of buildings was left to carpenters who undertook to interpret architectural manuals imported from England. There are an astonishing number of these handbooks for builders in colonial libraries, and the houses erected during the eighteenth century show their influence. Most domestic architecture of the first three-quarters of the eighteenth century displayed a wide range of taste and freedom of application of the rules laid down in these books.Increasing wealth throughout the colonies resulted in houses of improved design, whether the material was wood, stone or brick. New England still favored wood, though brick houses became common in Boston and other towns, where the danger of fire forced people to use more durable material. A few houses in New England were built of stone, but only in Pennsylvania and its neighboring areas was stone widely used in dwellings. An increased use of bricks is noticeable in Virginia and Maryland, but wood remained the most popular material even in houses built by wealthy landowners. In the Carolinas, even in the crowded town of Charleston, wooden houses were much more common than brick houses.Eighteenth-century houses showed great interior improvements over their predecessors. Windows were made larger and shutters (百叶窗) removed. Large, clear panes (玻璃窗) replaced the gray glass of the seventeenth century. Doorways were larger and more decorative. Fireplaces became decorative features of rooms. Walls were sometimes elaborately decorated. White paint began to take the place of blue, yellow, green and gray colors, which had been popular for walls in the earlier years. After about 1730, advertisements for wallpaper styles in scenic patterns began to appear in colonial newspapers. What does the passage mainly discuss
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