s="" survival="" that="" is="" at="" stake,="" conservationists="" say.="" unlike="" the="" endangered="" tiger,="" even="" great="" whales,="" african="" elephant="" in="" measure="" architect="" of="" its="" environment.="" as="" a="" voracious="" eater="" vegetation,="" it="" largely="" shapes="" forest-and-savanna="" surroundings="" which="" lives,="" thereby="" setting="" terms="" existence="" for="" millions="" other="" storied="" animals-from="" zebras="" to="" gazelles="" giraffes="" and="" wildebeests—that="" share="" habitat="" disappears,="" scientists="" say,="" many="" species="" will="" also="" disappear="" from="" vast="" stretches="" forest="" savanna,="" drastically="" altering="" impoverishing="" whole="" ecosystems.It is the elephant's metabolism and appetite that make it a disturber of the environment and therefore an important creator of habitat. In a constant search for the 300 pounds of vegetation it must have every day, it kills small trees and underbrush and pulls branches off big trees as high as its trunk will reach. This creates innumerable open spaces in both deep tropical forests and in the woodlands that cover part of the African savannas. The resulting patchwork, a mosaic of vegetation in various stages of regeneration, in turn creates a greater variety of forage that attracts a greater variety of other vegetation-eaters than would otherwise be the case.In studies over the last 20 years in southern Kenya near Mount Kilimanjaro, Dr.Western has found that when elephants are allowed to roam die savannas naturally and normally, they spread out at "intermediate densities." Their foraging creates a mixture of savanna woodlands (what the Africans call bush) and grassland. The result is a highly diverse array of other plant-eating species: those like the zebra, wildebeest and gazelle, that graze: those like the giraffe, bushbuck and lesser kudu, that browse on tender shoots, buds, twigs and leaves; and plant-eating primates like the baboon and vervet monkey. These herbivores attract carnivores like the lion and cheetah.When the elephant population thins out. Dr. Western said, the woodlands become denser and the grazers are squeezed out. When pressure from poachers forces elephants to crowd more densely onto reservations, the woodlands there are knocked out and the browsers and primates disappear.Something similar appears to happen in dense tropical rain forests. In their natural state, because the overhead forest canopy shuts out sunlight and prevents growth on the forest floor, rain forests provide slim pickings for large, hoofed plant-eaters. By pulling down trees and eating new growth, elephants enlarge natural openings in the canopy, allowing plants to regenerate on the forest floor and bringing down vegetation from the canopy so that smaller species can get at it.In such situations, the rain forest becomes hospitable to large plant-eating mammals such as bongos, bush pigs, duikers, forest hogs, swamp antelopes, forest buffaloes, okapis, sometimes gorillas and always a host of smaller animals that thrive on secondary growth. When elephants disappear and the forest reverts, the larger mammals give way to smaller, nimbler animals like monkeys, squirrels and rodents.1.The passage is primarily concerned with（ ）.2.In the opening paragraph, the author mentions tigers and whales in order to emphasize which point about the elephant?3.A necessary component of the elephant's ability to transform the landscape is its （ ）.4.It can be inferred from the passage that（ ）.5.Which of the following statements best expresses the authors attitude toward the damage to vegetation caused by foraging elephants?'>

The African elephant—mythic symbol of a continent, keystone of its ecology and the largest land animal remaining on earth—has become the object of one of the biggest, broadest international efforts yet mounted to turn a threatened species off the road to extinction. But it is not only the elephant's survival that is at stake, conservationists say. Unlike the endangered tiger, unlike even the gr

When traveling, you are advised to take travelers' checks, which provide a secure （ ） to carrying your money in cash.

If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation- conversion of liquid water to water vapor. In this manner, the salinity is increased, since the salts stay behind. If this is carried to the extreme, of course, white crystals of salt would be left behind.The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff.Normally, in tropical regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.In the Weddell Sea, off Antarctica, the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portions of the oceans of the world.1.According to the passage, the ocean generally has more salt in（ ） .2.The world “it” in line 4(paragraph 4) refers to（ ） .3.Why does the author mention the Weddell Sea?4.Which of the following is NOT a result of the formation of ocean ice?5.What can be inferred about the water near the bottom of oceans?

You and I don’t need anyone else’s assistance. We can solve these problems by（ ） .句意: 我和你都不需要其它任何人的帮助。我们靠我们自己可以解决问题。

Charles Darwin’s “On the Origin of Species” is credited with sparking evolution’s revolution in scientific thought, but many observers had pondered evolution before him. It was understanding the idea’s significance and selling it to the public that made Darwin great, according to the Arnold arboretum’s new director.William Friedman, the Arnold Professor of Organism and Evolutionary Biology who took over as arboretum director Jan.1 has studied Darwin’s writings as well as those of his predecessors and contemporaries. While Darwin is widely credited as the father of evolution, Friedman said the “historical sketch” that Darwin attached to later printings of his masterpiece was intended to mollify those who demanded credit for their own earlier ideas.The historical sketch grew with each subsequent printing, Friedman told an audience Monday (Jan. 10)，until, by the 6th edition, 34 authors were mentioned in it. Scholars now believe that somewhere between 50 and 60 authors had beaten Darwin in their writings about evolution. Included was Darwin’s grandfather, Erasmus Darwin, a physician who irritated clergymen with his insistence that life arose from lower forms, specifically mollusks.Friedman’s talk, “A Darwinian Look at Darwin’s Evolutionist Ancestors，” took place at the arboretum’s Hunnewell Building and was the first in a new Director’s Lecture Series.Though others had clearly pondered evolution before Darwin, he wasn’t without originality. Friedman said that Darwin’s thinking on natural selection as the mechanism of evolution was shared by few, most prominently Alfred Wallace, whose writing on the subject after years in the field spurred Darwin’s writing of “On the Origin of Species”. Although the book runs more than 400 pages, Friedman said it was never the book on evolution and natural selection that Darwin intended. In 1856, three years before the book was published, he began work on a detailed tome on natural selection that wouldn’t see publication until 1975.The seminal event in creating “On the Origin of Species” occurred in 1858, when Wallace wrote Darwin detailing Wallace’s ideas of evolution by natural selection. The arrival of Wallace’s ideas galvanized Darwin into writing “ On the Origin of Species ” as an “ abstract ” of the ideas he was painstakingly laying out in the larger work. This was a lucky break for Darwin, because it forced him to write his ideas in plain language, which led to a book that was not only revolutionary, despite those who’d tread similar ground before, but that was also very readable.Though others thought about evolution before Darwin, scientific discovery requires more than just an idea. In addition to the concept, discovery requires the understanding of the significance of the idea， something some of the earlier authors clearly did not have 一 such as the arborist who buried his thoughts on natural selection in the appendix of a book on naval timber. Lastly, scientific discovery demands the ability to convince others of the correctness of an idea. Darwin, through “On the Origin of Species，” was the only thinker of the time who had all three of those traits, Friedman said.“Darwin had the ability to convince others of the correctness of the idea，” Friedman said, adding that even Wallace, whose claim to new thinking on evolution and natural selection was stronger than all the others, paid homage to Darwin by titling his 1889 book on the subject, “ Darwinism. ’’

1.According to William Friedman, Darwin’s “On the Origin of Species” is great in that ______.

2.Friedman believes that Darwin attached a “historical sketch” to later printings of his book in an attempt to _______.

3.In Friedman’s view, Darwin’s originality lies in _______.

4.We have learned that at first Darwin intended to write his idea in（）

5.Scientific discovery required all the following Except（ ）

You said boys were cleverer than girls. That is（ ）I disagree.