破解托福阅读中的最难题型 ---- 小结题 / 图表题

1. 破解托福阅读中的最难题型----小结题/图表题 小马过河托福阅读老师白凤娇

3. 总结题的误区一 有人说：总结题选文章的主要观点， 一定是这样么？

4. Warm-up The Long-term Stability of Ecosystems

5. 1Plant communities assemble themselves flexibly, and their particular structure depends on the specific history of the area. Ecologists use the term “succession” to refer to the changes that happen in plant communities and ecosystems over time. The first community in a succession is called a pioneer community, while the long-lived community at the end of succession is called a climax community. Pioneer and successional plant communities are said to change over periods from 1 to 500 years. These changes—in plant numbers and the mix of species—are cumulative. Climax communities themselves change but over periods of time greater than about 500 years. 2 An ecologist who studies a pond today may well find it relatively unchanged in a year’s time. Individual fish may be replaced, but the number of fish will tend to be the same from one year to the next. We can say that the properties of an ecosystem are more stable than the individual organisms that compose the ecosystem.

6. 3 At one time, ecologists believed that species diversity made ecosystems stable. They believed that the greater the diversity the more stable the ecosystem. Support for this idea came from the observation that long-lasting climax communities usually have more complex food webs and more species diversity than pioneer communities. Ecologists concluded that the apparent stability of climax ecosystems depended on their complexity. To take an extreme example, farmlands dominated by a single crop are so unstable that one year of bad weather or the invasion of a single pest can destroy the entire crop. In contrast, a complex climax community, such as a temperate forest, will tolerate considerable damage from weather to pests.

7. 4 The question of ecosystem stability is complicated, however. The first problem is that ecologists do not all agree what “stability” means. Stability can be defined as simply lack of change. In that case, the climax community would be considered the most stable, since, by definition, it changes the least over time. Alternatively, stability can be defined as the speed with which an ecosystem returns to a particular form following a major disturbance, such as a fire. This kind of stability is also called resilience. In that case, climax communities would be the most fragile and the least stable, since they can require hundreds of years to return to the climax state.

8. 5 Even the kind of stability defined as simple lack of change is not always associated with maximum diversity. At least in temperate zones, maximum diversity is often found in mid-successional stages, not in the climax community. Once a redwood forest matures, for example, the kinds of species and the number of individuals growing on the forest floor are reduced. In general, diversity, by itself, does not ensure stability. Mathematical models of ecosystems likewise suggest that diversity does not guarantee ecosystem stability—just the opposite, in fact. A more complicated system is, in general, more likely than a simple system to break down. A fifteen-speed racing bicycle is more likely to break down than a child’s tricycle.

9. 6Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human activities. The destruction caused by the volcanic explosion of Mount St. Helens, in the northwestern United States, for example, pales in comparison to the destruction caused by humans. We need to know what aspects of a community are most important to the community’s resistance to destruction, as well as its recovery.

10. 7 Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the “patchiness” of the environment, an environment that varies from place to place supports more kinds of organisms than an environment that is uniform. A local population that goes extinct is quickly replaced by immigrants from an adjacent community. Even if the new population is of a different species, it can approximately fill the niche vacated by the extinct population and keep the food web intact.

11. 文章的主要观点： P1：介绍‘succession’ ‘pioneer community’‘cc’定义； P2：We can say that the properties of an ecosystem are more stable than the individual organisms that compose the ecosystem. P3：At one time, ecologists believed that species diversity made ecosystems stable

12. 4 The question of ecosystem stability is complicated, however. The first problem is that ecologists do not all agree what “stability” means. 5Even the kind of stability defined as simple lack of change is not always associated with maximum diversity.

13. 6Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human activities. 7 Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the “patchiness” of the environment

14. ○The changes that occur in an ecosystem from the pioneer to the climax community can be seen in one human generation. ○A high degree of species diversity does not always result in a stable ecosystem. ○The level of resilience in a plant community contributes to its long-term stability. ○Ecologists agree that climax communities are the most stable types of ecosystems. ○Disagreements over the meaning of the term “stability” make it difficult to identify the most stable ecosystems. ○The resilience of climax communities makes them resistant to destruction caused by humans.

15. 小结：应该看什么？ 首尾段的首尾句 如果段首一句和第二句有因果、转折的关系，都要读。 如果段首一句是例子，去段尾找观点

16. 总结题的误区二 有人说，总结题不选细节， 可是。。。

17. Geothermal Energy 1. Earth's internal heat, fueled by radioactivity, provides the energy for plate tectonics and continental drift, mountain building, and earthquakes. It can also be harnessed to drive electric generators and heat homes. Geothermal energy becomes available in a practical form when underground heat is transferred by water that is heated as it passes through a subsurface region of hot rocks (a heat reservoir) that may be hundreds or thousands of feet deep. The water is usually naturally occurring groundwater that seeps down along fractures in the rock; less typically, the water is artificially introduced by being pumped down from the surface. The water is brought to the surface, as a liquid or steam, through holes drilled for the purpose.

18. 2.By far the most abundant form of geothermal energy occurs at the relatively low temperatures of 80° to 180° centigrade. Water circulated through heat reservoirs in this temperature range is able to extract enough heat to warm residential, commercial, and industrial spaces. More than 20,000 apartments in France are now heated by warm underground water drawn from a heat reservoir in a geologic structure near Paris called the Paris Basin. Iceland sits on a volcanic structure known as the Mid-Atlantic Ridge. Reykjavik, the capital of Iceland, is entirely heated by geothermal energy derived from volcanic heat.

19. 3.Geothermal reservoirs with temperatures above 180° centigrade are useful for generating electricity. They occur primarily in regions of recent volcanic activity as hot, dry rock; natural hot water; or natural steam. The latter two sources are limited to those few areas where surface water seeps down through underground faults or fractures to reach deep rocks heated by the recent activity of molten rock material. The world's largest supply of natural steam occurs at The Geysers, 120 kilometers north of San Francisco, California. In the 1990s enough electricity to meet about half the needs of San Francisco was being generated there. This facility was then in its third decade of production and was beginning to show signs of decline, perhaps because of over development. By the late 1990s some 70 geothermal electric-generating plants were in operation in California, Utah, Nevada, and Hawaii, generating enough power to supply about a million people. Eighteen countries now generate electricity using geothermal heat.

20. 4.Extracting heat from very hot, dry rocks presents a more difficult problem: the rocks must be fractured to permit the circulation of water, and the water must be provided artificially. The rocks are fractured by water pumped down at very high pressures. Experiments are under way to develop technologies for exploiting this resource.

21. 5. Like most other energy sources, geothermal energy presents some environmental problems. The surface of the ground can sink if hot groundwater is withdrawn without being replaced. In addition, water heated geothermally can contain salts and toxic materials dissolved from the hot rock. These waters present a disposal problem if they are not returned to the ground from which they were removed.

22. 6.The contribution of geothermal energy to the world's energy future is difficult to estimate. Geothermal energy is in a sense not renewable, because in most cases the heat would be drawn out of a reservoir much more rapidly than it would be replaced by the very slow geological processes by which heat flows through solid rock into a heat reservoir. However, in many places (for example, California, Hawaii, the Philippines, Japan, Mexico, the rift valleys of Africa)the resource is potentially so large that its future will depend on the economics of production. At present, we can make efficient use of only naturally occurring hot water or steam deposits. Although the potential is enormous, it is likely that in the near future geothermal energy can make important local contributions only where the resource is close to the user and the economics are favorable, as they are in California, New Zealand, and Iceland. Geothermal energy probably will not make large-scale contributions to the world energy budget until well into the twenty-first century, if ever.

23. Heat reservoirs with a temperature from 80° to 180° centigrade can be used, as in France and Iceland, to heat buildings. • A number of countries now use geothermal reservoirs that contain water or steam above 180° centigrade to generate electricity. • Most heat reservoirs with a temperature above 180° centigrade cannot be used for energy because they are usually too close to recent volcanic activity. • The sinking of land above heat reservoirs and other environmental problems arise when water is pumped into a heat reservoir under high pressure. • Experiments are under way to determine if geothermally heated waters could be used as a source of certain minerals that have been dissolved out of hot rocks deep within Earth. • A number of issues, including how to extract heat from reservoirs that do not have a natural supply of water, will significantly limit the use of geothermal energy for the foreseeable future.

24. 总结题的奥秘 • 排除法 • 细节题 • 文章结构

25. 破解总结题一 排除法 初步排除信息明显错误的选项； 对应选项与原文；

26. 破解总结题二 细节题 Q2. According to paragraph 1, which of the following is NOT true of climax communities? 细节题选项：They remain stable for at least 500 years at a time. ○The changes that occur in an ecosystem from the pioneer to the climax community can be seen in one human generation.

27. Q6. According to paragraph 4, which of the following is true of climax communities? 细节题选项： They can be considered both the most and the least stable communities. ○Ecologists agree that climax communities are the most stable types of ecosystems

28. 破解总结题三 文章结构 总分结构（现象解释型：旧理论+新理论） 时间发展顺序结构 对比结构（多为图表题）

29. 结构特点 Introduction Background+ Topic(结构) Body Sub topic (结构)+ analysis/evidence Structure Conclusion Topic (结构)

30. Little is known about the stages of evolution during the Cambrian period, in part because early animals were soft bodied and could fossilize only under particular conditions. • While animal fossils from before the Cambrian explosion have no modern descendants, many animals that evolved during the Cambrian explosion can be assigned to modern groups. (BS) • Although the reasons for the rapid evolution of animals during the Cambrian period are not known, one proposed explanation is an abundance of niches with a lack of competitors.

31. Frontal lobe function of the brain may need to develop before memory retrieval can occur.（理论一） • The opportunity to hear chronologically narrated stories may help three-year-old children produce long-lasting memories.(理论二) • The contrasting ways in which young children and adults process information may determine their relative success in remembering.（理论三）

32. Recent discoveries of fossils have helped to show the link between land mammals and cetaceans. （A化石/1段） • The discovery of Ambulocetusnatans provided evidence for a whale that lived both on land and at sea.（A化石） • Fossils thought to be transitional forms between walking mammals and swimming whales were found.（A化石/1段）

33. Thomas Edison‘s design of the Kinetoscope inspired the development of large screen projection.（projection） • The development of projection technology made it possible to project images on a large screen（projection） • Once film images could be projected, the cinema became form of mass consumption. （projection）

34. Watt’s steam engine played a leading role in greatly increasing industrial production of all kinds.（对工业的影响） • In the mid-1700s James Watt transformed an inefficient steam pump into a fast, flexible, fuel-efficient engine.（Watt改善蒸汽机） • The availability of steam engines was a major factor in the development of railroads, which solved a major transportation problem.（对交通的影响）

35. 总结题TIPS 看title Headline 常常是introduction part，即文章的一二段 优先排除带有绝对词的选项，

36. The Long-term Stability of Ecosystems ○The changes that occur in an ecosystem from the pioneer to the climax community can be seen in one human generation. ○A high degree of species diversity does not always result in a stable ecosystem. ○The level of resilience in a plant community contributes to its long-term stability. ○Ecologists agree that climax communities are the most stable types of ecosystems. ○Disagreements over the meaning of the term “stability” make it difficult to identify the most stable ecosystems. ○The resilience of climax communities makes them resistant to destruction caused by humans.

37. The Long-term Stability of Ecosystems ○The changes that occur in an ecosystem from the pioneer to the climax community can be seen in one human generation. ○A high degree of species diversity does not always result in a stable ecosystem. ○The level of resilience in a plant community contributes to its long-term stability. ○Ecologists agree that climax communities are the most stable types of ecosystems. ○Disagreements over the meaning of the term “stability” make it difficult to identify the most stable ecosystems. ○The resilience of climax communities makes them resistant to destruction caused by humans.

38. 图表题

39. 图表题 文章多为对比（A vs. B）结构 建议回到原文找到过渡段； 选择正确信息，归类

40. Opportunists and Competitors 看各段句首，找过渡段 全文共7段 第7段段首为The opposite of an opportunist is a competitor.

41. Swimming Machines 第八段（过渡段） There are adaptations that increase the amount of forward thrust as well as those that reduce drag. ○The absence of scales from most of the body ○The ability to take advantage of eddies ○The ability to feed and reproduce while swimming ○Eyes that do not protrude ○Fins that are stiff, narrow, and smooth ○The habit of swimming with the mouth open ○A high, narrow tail with swept-back tips

42. Geology and Landscape 第四段（过渡段） There are adaptations that increase the amount of forward thrust as well as those that reduce drag. ○Collision of Earth's crustal plates ○Separation of continents ○Wind-driven sand ○Formation of grass roots in soil ○Earthquakes ○Volcanic activity ○Weather processes

43. 信息正确是王道！ 主要信息

44. TOEFL 必胜！