托福OG阅读电子版-clear.doc

(完整版)托福OG阅读电子版 clear
Applied Arts and Fine Arts
Although we now tend to refer to the various crafts according to the materials used to construct them—clay， glass， wood， fiber, and metal—it was once common to think of crafts in terms of function， which led to their being known as the “applied arts.” Approaching crafts from the point of view of function， we can divide them into simple categories: containers， shelters, and supports。 There is no way around the fact that containers， shelters, and supports must be functional。 The applied arts are thus bound by the laws of physics, which pertain to both the materials used in their making and the substances and things to be contained, supported， and sheltered. These laws are universal in their application, regardless of cultural beliefs, geography， or climate. If a pot has no bottom or has large openings in its sides, it could hardly be considered a container in any traditional sense. Since the laws of physics, not some arbitrary decision， have determined the general form of applied—art objects, they follow basic patterns， so much so that functional forms can vary only within certain limits. Buildings without roofs， for example, are unusual because they depart from the norm. However, not all functional objects are exactly alike; that is why we recognize a Shang Dynasty vase as being different from an Inca vase. What varies is not the basic form but the incidental details that do not obstruct the object’s primary function.
Sensitivity to physical laws is thus an important consideration for the maker of applied-art objects. It is often taken for granted that this is also true for the maker of fine—art objects. This assumption misses a significant difference between the two disciplines。 Fine-art objects are not constrained by the laws of physics in the same way that applied-art objects are。 Because their primary purpose is not functional， they are only limited in terms of the materials used to make them. Sculptures must, for example， be stable, which requires an understanding of the properties of mass, weight distribution， and stress。 Paintings must have rigid stretchers so that the canvas will be taut， and the paint must not deteriorate, crack， or discolor. These are problems that must be overcome by the artist because they tend to intrude upon his or her conception of the work. For example， in the early Italian Renaissance, bronze statues of horses with a raised foreleg usually had a cannonball under that hoof。 This was done because the cannon ball was needed to support the weight of the leg。 In other words, the demands of the laws of physics, not the sculptor’s aesthetic intentions, placed the ball there. That this device was a necessary structural compromise is clear from the fact that the cannonball quickly disappeared when sculptors learn how to strengthen internal structure of a statue with iron braces (iron being much stronger than bronze）.
Even though the fine arts in the twentieth century often treat materials in new ways, the basic difference in attitude of artists in relation to their materials in the fine arts and the applied arts remains relatively constant. It would therefore not be too great an exaggeration to say that practitioners of the fine arts work to overcome the limitations of their materials, whereas those engaged in the applied arts work in concert with their materials.

The Origins of Cetaceans
It should be obvious that cetaceans—whales, porpoises， and dolphins-are mammals. They breathe through lungs， not through gills, and give birth to live young. Their streamlined bodies， the absence of hind legs， and the presence of a fluke and blowhole cannot disguise their affinities with land—dwelling mammals. However， unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea）， it is not easy to envision what the first whales looked like。 Extinct but already fully marine cetaceans are known from the fossil record. How was the gap between a walking mammal and a swimming whale bridged？ Missing until recently were fossils clearly intermediate， or transitional， between land mammals and cetaceans。
Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans。 In 1979， a term looking for fossils in northern Pakistan found what proved to be the oldest fossil whale. The fossil was officially named Pakicetus in honor of the country where the discovery was made. Pakicetus was found embedded in rocks formed from river deposits that were 52 million years old. The river that formed these deposits was actually not far from an ancient ocean known as the Tethys Sea。
The fossil consists of a complete skull of an archaeocyte， an extinct group of ancestors of modern cetaceans。 Although limited to a skull， the Pakicetus fossil provides precious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack the enlarged space that is filled with fat or oil and used for receiving underwater sound in modern whales. Pakicetus probably detected sound through the ear opening as in land mammals. The skull also lacks a blowhole, another cetacean adaptation for diving。 Other features, however， show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids， and cetaceans. It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean。 It probably bred and gave birth on land.
Another major discovery was made in Egypt in 1989。 Several skeletons of another early whale, Basilosaurus， were found in sediments left by the Tethys Sea and now exposed in the Sahara desert. This whale lived around 40 million years ago, 12 million years after Pakicetus. Many incomplete skeletons were found but they included， for the first time in an archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs would have been far too small to have supported the 50—foot-long Basilosaurus on land。 Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional， or vestigial, hind legs。
An even more exciting find was reported in 1994， also from Pakistan。 The now extinct whale Ambulocetus natans (“the walking whale that swam”） lived in the Tethys Sea 49 million years ago。 It lived around 3 million years after Pakicetus but 9 million before Basilosaurus. The fossil luckily includes a good portion of the hind legs. The legs were strong and ended in long feet very much like those of a modern pinniped。 The legs were certainly functional both on land and at sea. The whale retained a tail and lacked a fluke， the major means of locomotion in modern cetaceans. The structure of the backbone shows, however, that ambulocetus swam like modern whales by moving the rear portion of its body up and down， even though a fluke was missing。 The large hind legs were used for propulsion in water. On land， where it probably bred and gave birth， Ambulocetus may have moved around very much like a modern sea lion。 It was undoubtedly a whale that linked life on land with life at sea。
1. In paragraph 1， what does the author say about the presence of a blowhole in cetaceans?
A It clearly indicates that cetaceans are mammals。
B It cannot conceal the fact that cetaceans are mammals.
C It is the main different between cetaceans and land—dwelling mammals.
D It cannot yield clues about the origins of cetaceans.
2. Which of the following can be inferred from paragraph 1 about early sea otters?
A It is not difficult to imagine what they looked like.
B There were great numbers of them。
C They lived in the sea only.
D They did not leave many fossil remains。
3. The word precious in the passage is closest in meaning to
A exact
B scarce
C valuable
D initial
4. Pakicetus and modern cetaceans have similar
A hearing structures
B adaptations for diving
C skull shapes
D breeding locations
5. The word it in the passage refers to
A Pakicetus
B fish
C life
D ocean
6. The word exposed in the passage is closest in meaning to
A explained
B visible
C identified
D located
7. The hind leg of Basilosaurus was a significant find because it showed that Basilosaurus
A lived later than Ambulocetus natans
B lived at the same time as Pakicetus
C was able to swim well
D could not have walked on land
8. It can be inferred that Basilosaurus bred and gave birth in which of the following locations?
A on land
B both on land and at sea
C in a shallow water
D in a marine environment
9. Why does the author use the word luckily in mentioning that the Ambulocetus natans fossil included hind legs?
A Fossil legs of early whales are a rare find.
B The legs provided important information about the evolution of cetaceans。
C The discovery allowed scientist to reconstruct a complete skeleton of the whale。
D Until that time， only the front legs of early had been discovered。
10. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
A Even though Ambulocetus swam by moving its body up and down， it did not have a backbone.
B The backbone of Ambulocetus， which allowed it to swim, provides evidence of its missing fluke。
C Although Ambulocetus had no fluke, its back bone structure shows that it swam like modern whales.
D By moving the rear parts of their bodies up and down, modern whales swim in a different way from the way Ambulocetus swam。
11. The word propulsion in the passage is closest in meaning to
A staying afloat
B changing direction
C decreasing weight
D moving forward
12. Look at the four squares ［ ］ that indicate where the following sentence can be added to the passage。
This is a question that has puzzled scientists for ages。
Where would the sentence best fit？
13—14。 Directions： An introductory sentence for a brief summary of the passage is provided below。 Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage。 Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage。 This question is worth 2 points。
This passage discusses fossils that help to explain the likely origins of cetaceans-whales, porpoises， and dolphins。

1. Recent discoveries of fossils have helped to show the link between land mammals and cetaceans.
2. The discovery of Ambulocetus natans provided evidence for a whale that lived both on land and at sea。
3. The skeleton of Basilosaurus was found in what had been the Tethys Sea, an area rich in fossil evidence.
4. Pakicetus is the oldest fossil whale yet to be found.
5. Fossils thought to be transitional forms between walking mammals and swimming whales were found。
6. Ambulocetus’s hind legs were used for propulsion in the water。

Desert Formation
The deserts， which already occupy approximately a fourth of the Earth’s land surface, have in recent decades been increasing at an alarming pace. The expansion of desertlike conditions into areas where they did not previously exist is called desertification. It has been estimated that an additional one—fourth of the Earth's land surface is threatened by this process。
Desertification is accomplished primarily through the loss of stabilizing natural vegetation and the subsequent accelerated erosion of the soil by wind and water。 In other cases， the finer particles may be removed， while the sand-sized particles are accumulated to form mobile hills or ridges of sand.
Even in the areas that retain a soil cover， the reduction of vegetation typically results in the loss of the soil’s ability to absorb substantial quantities of water. The impact of raindrops on the loose soil tends to transfer fine clay particles into the tiniest soil spaces, sealing them and producing a surface that allows very little water penetration。 Water absorption is greatly reduced; consequently runoff is increased, resulting in accelerated erosion rates。 The gradual drying of the soil caused by its diminished ability to absorb water results in the further loss of vegetation， so that a cycle of progressive surface deterioration is established.
In some regions， the increase in desert areas is occurring largely as the result of a trend toward drier climatic conditions。 Continued gradual global warming has produced an increase in aridity for some areas over the past few thousand years. The process may be accelerated in subsequent decades if global warming resulting from air pollution seriously increases.
There is little doubt， however， that desertification in most areas results primarily from human activities rather than natural processes。 The semiarid lands bordering the deserts exist in a delicate ecological balance and are limited in their potential to adjust to increased environmental pressures。 Expanding populations are subjecting the land to increasing pressures to provide them with food and fuel。 In wet periods， the land may be able to respond to these stresses. During the dry periods that are common phenomena along the desert margins, though, the pressure on the land is often far in excess of its diminished capacity， and desertification results。
Four specific activities have been identified as major contributors to the desertification processes： overcultivation, overgrazing, firewood gathering， and overirrigation. The cultivation of crops has expanded into progressively drier regions as population densities have grown. These regions are especially likely to have periods of severe dryness, so that crop failures are common. Since the raising of most crops necessitates the prior removal of the natural vegetation， crop failures leave extensive tracts of land devoid of a plant cover and susceptible to wind and water erosion。
The raising of livestock is a major economic activity in semiarid lands， where grasses are generally the dominant type of natural vegetation。 The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil。 This is usually followed by the drying of the soil and accelerated erosion.
Firewood is the chief fuel used for cooking and heating in many countries. The increased pressures of expanding populations have led to the removal of woody plants so that many cities and town are surrounded by large areas completely lacking in trees and shrubs。 The increasing use of dried animal waste as a substitute fuel has also hurt the soil because this valuable soil conditioner and source of plant nutrients is no longer being returned to the land.
The final major human cause of desertification is soil salinization res