Egypt Felled by Famine Even ancient Egypt’ s mighty pyramid builders were powerless in the face of the famine that helped bring down their civilization around 2180 BC. Now evidence gleaned(搜集)from mud deposited by the River Nile suggests that a shift in climate thousands of kilometers to the south was ultimately to blame—and the same or worse could happen today. The ancient Egyptians depended on the Nile’ s annual floods to irrigate their crops. But any change in climate that pushed the African monsoons(季风)southwards out of Ethiopia would have diminished these floods. Dwindling(使减少)rains in the Ethiopian highlands would have meant fewer plants to establish the soil. When rain did fall it would have washed large amounts of soil into the Blue Nile and into Egypt, along with sediment(沉积物)from the White Nile. The Blue Nile mud has a different isotope(同位素)signature from that of the White Nile. So by analyzing isotope differences in mud deposited in the Nile Delta, Michael Krom of Leeds University worked out what proportion of sediment came from each branch of the river. Krom reasons that during periods of drought, the amount of the Blue Nile mud in the river would be relatively high. He found that one of these periods, from 4, 500 to 4, 200 years ago, immediately predated the fall of the Egypt’ s old Kingdom. The weakened waters would have been catastrophic for the Egyptians. “ Changes that affect food supply don’ t have to be very large to have a ripple effect in societies, “ says Bill Ryan of the Lamont Doherty Earth Observatory(天文台)in New York. “Similar events today could be even more devastating, “ says team member Daniel Stanley, a geoarchaeologist from the Smithsonian Institution in Washington, D. C. “Anything humans do to shift the climate belts would have an even worse effect along the Nile system because the populations have increased dramatically. “

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Plants in Desert Only special plants can survive the terrible climate of a desert, for these are regions where the annual range of the soil temperature can be over 75 °C . Furthermore, during the summer there are few clouds in the sky to protect plants from the sun’ s ray. Another problem is the fact that there are frequently strong winds that drive small, sharp particles of sand into the plants, tearing and damaging them. The most difficult problem for all forms of plant life, however, is the fact that the entire annual rainfall occurs during a few days or weeks in spring. Grasses and flowers in desert survive from one year to the next by existing through the long, hot, dry season in the form of seeds. These seeds remain inactive unless the right amount of rain falls. If no rain falls, or if insufficient rain falls, they wait until the next year, or even still the next. Another factor that helps these plants to survive is the fact that their life cycles are short. By the time the water from the spring rains disappears—just a few weeks after it falls—such plants no longer need any. The perennials(多年生植物)have special features that enable them to survive as plants for several years. Thus, nearly all desert perennials have extensive root systems below ground and a small shoot system above ground. The large root network enables the plant to absorb as much water as possible in short time. The small shoot system, on the other hand, considerably limits water loss by evaporation(蒸发). Another feature of many perennials is that after the rainy season they lose their leaves in preparation for the long, dry season, just as trees in wetter climates lose theirs in preparation for the winter. This reduces their water loss by evaporation during the dry season. Then, in next rainy season, they come fully alive once more, and grow new branches, leaves and flowers, just as the grasses and flowers in desert do.

Science Fiction 1 Amongst the most popular books being written today are those which are usually classified as science fiction. Hundreds of titles are published every year and are read by all kinds of people. Furthermore, some of the most successful films of recent years have been based on science fiction stories. 2 It is often thought that science fiction is a fairly new development in literature, but its ancestors can be found in books written hundreds of years ago. These books were often concerned with the presentation of some form of ideal society, a theme which is still often found in modern stories. 3 Most of the classics of science fiction, however, have been written within the last hundred years. Books by writers such as Jules Verne and H. G. Wells, to mention just two well-known authors, have been translated into many languages. 4 Modern science fiction writers don’t write about men from Mars(火星)or space adventure stories. They are more interested in predicting the results of technical developments on society and the human mind; or in imagining future worlds which are a reflection of the world which we live in now. Because of this, their writing has obvious political undertones(含义). 5 In an age where science fact frequently overtakes(超过)science fiction, the writers may find it difficult to keep ahead of scientific advances. Those who are sufficiently clear-sighted to see the way we are going, however, may provide a valuable lesson on how to deal with the problems which society will inevitably face as it tries to master its new technology. A. Popularity of Science Fiction B. A Fairly New Development C. Classics of Science Fiction D. Difficulty in Keeping Ahead of Scientific Adventure E. Its Origin F. Themes of Modern Science Fiction

A. concerned with the problems to solve in the future B. to keep ahead of scientific advances C. have political implication D. a current theme E. read worldwide F. a recurrent theme

Older Volcanic Eruptions Volcanoes were more destructive in ancient history, not because they were bigger, but because the carbon dioxide they released wiped out life with greater ease. Paul Wignall from the University of Leeds was investigating the link between volcanic eruptions and mass extinctions. Not all volcanic eruptions killed off large numbers of animals, but all the mass extinctions over the past 300 million years coincided with huge formations of volcanic rock. To his surprise, the older the massive volcanic eruptions were, the more damage they seemed to do. He calculated the “killing efficiency“ for these volcanoes by comparing the proportion of life they killed off with the volume of lava(熔岩)that they produced. He found that size for size, older eruptions were at least 10 times as effective at wiping out life as their more recent rivals. The Permian(二叠纪)extinction, for example, which happened 250 million years ago, is marked by floods of volcanic rock in Siberia that cover an area roughly the size of western Europe. Those volcanoes are thought to have pumped out about 10 gigatonnes(十亿吨)of carbon as carbon dioxide. The global warming that followed wiped out 80 percent of all marine genera(种类)at the time, and it took 5 million years for the planet to recover. Yet 60 million years ago, there was another huge amount of volcanic activity and global warming but no mass extinction. Some animals did disappear but things returned to normal within ten thousands of years. “The most recent ones hardly have an effect at all, “ Wignall says. He ignored the extinction which wiped out the dinosaurs 65 million years ago, because many scientists believe it was primarily caused by the impact of an asteroid(小行星). He thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO₂. Vincent Courtillot, director of the Paris Geophysical Institute in France, says that Wignall’ s idea is provocative. But he says it is incredibly hard to do these sorts of calculations. He points out that the killing power of volcanic eruptions depends on how long they lasted. And it is impossible to tell whether the huge blasts lasted for thousands or millions of years. He also adds that it is difficult to estimate how much lava prehistoric volcanoes produced, and that lava volume may not necessarily correspond to carbon dioxide emissions.

The Greatest Mystery of Whales The whale is a warm-blooded, air-breathing animal, giving birth to its young alive, sucking them—and, like all mammals, originated on land. There are many【C1】______of this. Its front flippers(鳍状肢), used for steering and stability, are traces of feet. Immense strength is【C2】______into the great body of the big whales, and in fact most of a whale’ s body is one gigantic muscle. The blue whale’ s pulling strength has been estimated【C3】______ 400 horsepower. One specimen was reported to have towed(拖)a whaling vessel for seven hours at the【C4】______of eight knot(节). An angry whale will【C5】______. A famous example of this was the fate of Whaler Essex, 【C6】______was sunk off the coast of South America early in the last century. More recently, steel ships have【C7】______their plates buckled(使弯曲)in the same way. Sperm whales(抹香鲸)were known to seize the old-time whaleboats in their jaws and crush them. The greatest【C8】______of whales is their diving ability. The sperm whale dives to the bottom for his【C9】______food, the octopus(章鱼). In that search he is known to go as far down as 3, 200 feet, where the【C10】______is 1, 400 pounds to a square inch. Doing so he will【C11】______ underwater as long as one hour. Two special skills are involved in this storing up enough【C12】______ (all whales are air-breathed)and tolerating the great change in pressure. Just how he does it scientists have not【C13】______. It is believed that some of the oxygen is stored in a special【C14】______of blood vessels, rather than just held in the lungs. And it is believed that a special kind of oil in his head is some sort of a compensating mechanism that【C15】______adjusts the internal pressure of his body. But since you can’t bring a live whale into the laboratory for study, no one knows just how these things work.

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Egypt Felled by Famine Even ancient Egypt’ s mighty pyramid builders were powerless in the face of the famine that helped bring down their civilization around 2180 BC. Now evidence gleaned(搜集)from mud deposited by the River Nile suggests that a shift in climate thousands of kilometers to the south was ultimately to blame—and the same or worse could happen today. The ancient Egyptians depended on the Nile’ s annual floods to irrigate their crops. But any change in climate that pushed the African monsoons(季风)southwards out of Ethiopia would have diminished these floods. Dwindling(使减少)rains in the Ethiopian highlands would have meant fewer plants to establish the soil. When rain did fall it would have washed large amounts of soil into the Blue Nile and into Egypt, along with sediment(沉积物)from the White Nile. The Blue Nile mud has a different isotope(同位素)signature from that of the White Nile. So by analyzing isotope differences in mud deposited in the Nile Delta, Michael Krom of Leeds University worked out what proportion of sediment came from each branch of the river. Krom reasons that during periods of drought, the amount of the Blue Nile mud in the river would be relatively high. He found that one of these periods, from 4, 500 to 4, 200 years ago, immediately predated the fall of the Egypt’ s old Kingdom. The weakened waters would have been catastrophic for the Egyptians. “ Changes that affect food supply don’ t have to be very large to have a ripple effect in societies, “ says Bill Ryan of the Lamont Doherty Earth Observatory(天文台)in New York. “Similar events today could be even more devastating, “ says team member Daniel Stanley, a geoarchaeologist from the Smithsonian Institution in Washington, D. C. “Anything humans do to shift the climate belts would have an even worse effect along the Nile system because the populations have increased dramatically. “

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Why does the author mention “pyramid builders“?

Which of the following factors was ultimately responsible for the fall of the civilization of ancient Egypt?

Which of the following statements is true?

According to Krom, Egypt’ s Old Kingdom fell ______.

The word “devastating“ in the last paragraph could be best replaced by