托福阅读真题练习3篇

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托福阅读真题练习 篇1

The Long-Term Stability of Ecosystems

Plantmunities 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 plantmunities and ecosystems over time. The firstmunity in a succession is called a pioneermunity, while the long-livedmunity at the end of succession is called a climaxmunity. Pioneer and successional plantmunities are said to change over periods from 1 to 500 years. These changes—in plant numbers and the mix of species—are cumulative. Climaxmunities themselves change but over periods of time greater than about 500 years.

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 thatpose the ecosystem.

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 climaxmunities usually have moreplex food webs and more species diversity than pioneermunities. Ecologists concluded that the apparent stability of climax ecosystems depended on theirplexity. 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, aplex climaxmunity, such as a temperate forest, will tolerate considerable damage from weather to pests.

The question of ecosystem stability isplicated, 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 climaxmunity 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, climaxmunities would be the most fragile and the least stable, since they can require hundreds of years to return to the climax state.

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 climaxmunity. 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 moreplicated 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.

Ecologists are especially interested to know what factors contribute to the resilience ofmunities because climaxmunities 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 inparison to the destruction caused by humans. We need to know what aspects of amunity are most important to themunity’s resistance to destruction, as well as its recovery.

Many ecologists now think that the relative long-term stability of climaxmunitieses 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 adjacentmunity. 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.

Paragraph 1: Plantmunities 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 plantmunities and ecosystems over time. The firstmunity in a succession is called a pioneermunity, while the long-livedmunity at the end of succession is called a climaxmunity. Pioneer and successional plantmunities are said to change over periods from 1 to 500 years. These changes—in plant numbers and the mix of species—are cumulative. Climaxmunities themselves change but over periods of time greater than about 500 years.

1. The word “particular” in the passage is closest in meaning to

○Natural

○Final

○Specific

○Complex

2. According to paragraph 1, which of the following is NOT true of climaxmunities?

○They occur at the end of a succession.

○They last longer than any other type ofmunity.

○The numbers of plants in them and the mix of species do not change.

○They remain stable for at least 500 years at a time.

Paragraph 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 thatpose the ecosystem.

3. According to paragraph 2, which of the following principles of ecosystems can be learned by studying a pond?

○Ecosystem properties change more slowly than individuals in the system.

○The stability of an ecosystem tends to change as individuals are replaced.

○Individual organisms are stable from one year to the next.

○A change in the members of an organism does not affect an ecosystem’s properties

Paragraph 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 climaxmunities usually have moreplex food webs and more species diversity than pioneermunities. Ecologists concluded that the apparent stability of climax ecosystems depended on theirplexity. 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, aplex climaxmunity, such as a temperate forest, will tolerate considerable damage from weather of pests.

4. According to paragraph 3, ecologists once believed that which of the following illustrated the most stable ecosystems?

○Pioneermunities

○Climaxmunities

○Single-crop farmlands

○Successional plantmunities

Paragraph 4: The question of ecosystem stability isplicated, 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 climaxmunity 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, climaxmunities would be the most fragile and the least stable, since they can require hundreds of years to return to the climax state.

5. According to paragraph 4, why is the question of ecosystem stabilityplicated?

○The reasons for ecosystem change are not always clear.

○Ecologists often confuse the word “stability” with the word “resilience.”

○The exact meaning of the word “stability” is debated by ecologists.

○There are many different answers to ecological questions.

6. According to paragraph 4, which of the following is true of climaxmunities?

○They are more resilient than pioneermunities.

○They can be considered both the most and the least stablemunities.

○They are stable because they recover quickly after major disturbances.

○They are the most resilientmunities because they change the least over time.

Paragraph 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 climaxmunity. 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 moreplicated 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.)

7. Which of the following can be inferred from paragraph 5 about redwood forests?

○They be less stable as they mature.

○They support many species when they reach climax.

○They are found in temperate zones.

○They have reduced diversity during mid-successional stages.

托福阅读真题练习 篇2

When Jules Verne wrote Journey to the Center of the Earth in 1864， there were many conflicting theories about the nature of the Earths interior. Some geologists thought that it contained a highlypressed ball of incandescent gas， while others suspected that it consisted of separate shells， each made of a different material. Today， well over a century later， there is still little direct evidence of what lies beneath our feet. Most of our knowledge of the Earths interiores not from mines or boreholes， but from the study of seismic waves - powerful pulses of energy released by earthquakes.

The way that seismic waves travel shows that the Earths interior is far from uniform. The continents and the seabed are formed by the crust - a thin sphere of relatively light， solid rock. Beneath the crust lies the mantle， a very different layer that extends approximately halfway to the Earths center. There the rock is the subject of a battle between increasing heat and growing pressure.

In its high levels， the mantle is relatively cool; At greater depths， high temperatures make the rock behave more like a liquid than a solid. Deeper still， the pressure is even more intense， preventing the rock from melting in spite of a higher temperature.

Beyond a depth of around 2，900 kilometers， a great change takes place and the mantle gives way to the core. Some seismic waves cannot pass through the core and others are bent by it. From this and other evidence， geologists conclude that the outer core is probably liquid， with a solid center. It is almost certainly made of iron， mixed with smaller amounts of other elements such as nickel.

The conditions in the Earths core make it a far more alien world than space. Its solid iron heart is subjected to unimaginable pressure and has a temperature of about 9，000oF. Although scientists can speculate about its nature， neither humans nor machines will ever be able to visit it.

1. The word "conflicting" in line 2 is closest in meaning to（）

(A) controlling

(B) outdated

(C) opposing

(D) important

2. What is todays richest source of information about the Earths interior for geologists?（）

(A) Boreholes

(B) Shells

(C) Seismic waves

(D) Mines

3. The word "There" in line 16 refers to the （）

（A） mantle

（B） crust

（C） seabed

（D） Earth‘s center.

4. Which of the following is a primary characteristic of the Earth‘s mantle？（）

（A） Light， solid rock

（B） Uniformity ofposition

（C） Dramatically increasing pressure

（D） Compressed， incandescent gas

5. The phrase "gives way to" in line 24 is closest in meaning to（）

（A） runs along

（B） rubs against

（C） turns into

（D） floats on

6. The word "it" in line 26 refers to（）

（A） mantle

（B） core

（C） change

（D） depth

7. Why does the author state in line 30－31 that the Earth‘s core is "more alien" than space？

（A） Government funds are not available to study the Earth‘s core.

（B） Scientists aren‘t interested in the characteristics of the Earth‘s core.

（C） It is impossible to go to the Earth‘s core to do research.

（D） The Earth‘s core is made of elements that are dangerous to humans.

8. The word "speculate" in line 33 is closest in meaning to

（A） report

（B） learn

（C） worry

（D） hypothesize

托福阅读真题练习 篇3

The Rise of Teotihuacán

1 The city of Teotihuacán, which lay about 50 kilometers northeast of modern-day Mexico City, began its growth by 200–100 At its height, between about 150 and 700, it probably had a population of more than 125,000 people and covered at least 20 square kilometers. It had over 2,000 apartmentplexes, a great market, a large number of industrial workshops, an administrative center, a number of massive religious edifices, and a regular grid pattern of streets and buildings. Clearly, much planning and central control were involved in the expansion and ordering of this great metropolis. Moreover, the city had economic and perhaps religious contacts with most parts of Mesoamerica (modern Central America and Mexico).

2 How did this tremendous development take place, and why did it happen in the Teotihuacán Valley? Among the main factors are Teotihuacán’s geographic location on a natural trade route to the south and east of the Valley of Mexico, the obsidian1 resources in the Teotihuacán Valley itself, and the valley’s potential for extensive irrigation. The exact role of other factors is much more difficult to pinpoint—for instance, Teotihuacán’s religious significance as a shrine, the historical situation in and around the Valley of Mexico toward the end of the first millennium , the ingenuity and foresightedness of Teotihuacán’s elite, and, finally, the impact of natural disasters, such as the volcanic eruptions of the late first millennium

3 This last factor is at least circumstantially implicated in Teotihuacán’s rise. Prior to 200 , a number of relatively small centers coexisted in and near the Valley of Mexico. Around this time, the largest of these centers, Cuicuilco, was seriously affected by a volcanic eruption, with much of its agricultural land covered by lava. With Cuicuilco eliminated as a potential rival, any one of a number of relatively modest towns might have emerged as a leading economic and political power in Central Mexico. The archaeological evidence clearly indicates, though, that Teotihuacán was the center that did arise as the predominant force in the area by the first century

4 It seems likely that Teotihuacán’s natural resources—along with the city elite’s ability to recognize their potential—gave the city apetitive edge over its neighbors. The valley, like many other places in Mexican and Guatemalan highlands, was rich in obsidian. The hard volcanic stone was a resource that had been in great demand for many years, at least since the rise of the Olmecs (a people who flourished between 1200 and 400 ), and it apparently had a secure market. Moreover, recent research on obsidian tools found at Olmec sites has shown that some of the obsidian obtained by the Olmecs originated near Teotihuacán. Teotihuacán obsidian must have been recognized as a valuablemodity for many centuries before the great city arose.

5 Long-distance trade in obsidian probably gave the elite residents of Teotihuacán access to a wide variety of exotic goods, as well as a relatively prosperous life. Such success may have attracted immigrants to Teotihuacán. In addition, Teotihuacán’s elite may have consciously attempted to attract new inhabitants. It is also probable that as early as 200 Teotihuacán may have achieved some religious significance and its shrine (or shrines) may have served as an additional population magnet. Finally, the growing population was probably fed by increasing the number and size of irrigated fields.

6 The picture of Teotihuacán that emerges is a classic picture of positive feedback among obsidian mining and working, trade, population growth, irrigation, and religious tourism. The thriving obsidian operation, for example, would necessitate more miners, additional manufacturers of obsidian tools, and additional traders to carry the goods to new markets. All this led to increased wealth, which in turn would attract more immigrants to Teotihuacán. The growing power of the elite, who controlled the economy, would give them the means to physically coerce people to move to Teotihuacán and serve as additions to the labor force. More irrigation works would have to be built to feed the growing population, and this resulted in more power and wealth for the elite.

Directions: Answer the questions.

1. In paragraph 1, each of the following is mentioned as a feature of the city of Teotihuacán between 150 and 700 EXCEPT

A regularly arranged streets

B several administrative centers spread across the city

C many manufacturing workshops

D apartmentplexes

2. The word “ingenuity” in paragraph 2 is closest in meaning to

A ambition

B sincerity

C faith

D cleverness

3. Which of the following is NOT mentioned in paragraph 2 as a main factor in the development of Teotihuacán?

A The presence of obsidian in the Teotihuacán Valley

B The potential for extensive irrigation of Teotihuacán Valley lands

C A long period of volcanic inactivity in the Teotihuacán Valley

D Teotihuacán’s location on a natural trade route

4. What can be inferred from paragraph 3 about Cuicuilco prior to 200 ?

A It was a fairly small city until that date.

B It was located outside the Valley of Mexico.

C It emerged rapidly as an economical and political center.

D Its economy relied heavily on agriculture.

5. Which of the following allowed Teotihuacán to have “apetitive edge over its neighbors”?

A A well-exploited and readily availablemodity

B The presence of a highly stable elite class

C Knowledge derived directly from the Olmecs about the art of toolmaking

D Scarce natural resources in nearby areas such as those located in what are now the Guatemalan and Mexican highlands

6. According to paragraph 4, what has recent research on obsidian tools found at Olmec sites shown?

A Obsidian’s value was understood only when Teotihuacán became an important city.

B The residents of Teotihuacán were sophisticated toolmakers.

C The residents of Teotihuacán traded obsidian with the Olmecs as early as 400

D Some of the obsidian used by the Olmecs came from the area around Teotihuacán.

7. Select the TWO answer choices that are mentioned in paragraph 5 as being features of Teotihuacán that may have attracted immigrants to the city. To receive credit, you must select TWO answers.

A The prosperity of the elite

B Plenty of available housing

C Opportunities for well-paid agricultural employment

D The presence of one or more religious shrines

8. In paragraph 6, the author discusses “The thriving obsidian operation” in order to

A explain why manufacturing was the main industry of Teotihuacán

B give an example of an industry that took very little time to develop in Teotihuacán

C illustrate how several factors influenced each other to make Teotihuacán a powerful and wealthy city

D explain how a successful industry can be a source of wealth and a source of conflict at the same time

9. In paragraph 1 of the passage, there is a missing sentence. The paragraph is repeated below and shows four letters (A, B, C, and D) that indicate where the following sentence could be added.

In fact, artifacts and pottery from Teotihuacán have been discovered in sites as far away as the Mayan lowlands, the Guatemalan highlands, northern Mexico, and the Gulf Coast of Mexico.

Where would the sentence best fit?

The city of Teotihuacán, which lay about 50 kilometers northeast of modern-day Mexico City, began its growth by 200–100 At its height, between about 150 and 700, it probably had a population of more than 125,000 people and covered at least 20 square kilometers. (A) It had over 2,000 apartmentplexes, a great market, a large number of industrial workshops, an administrative center, a number of massive religious edifices, and a regular grid pattern of streets and buildings. (B) Clearly, much planning and central control were involved in the expansion and ordering of this great metropolis. (C) Moreover, the city had economic and perhaps religious contacts with most parts of Mesoamerica (modern Central America and Mexico). (D)

A Option A

B Option B

C Option C

D Option D

10. 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 sentences 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.

Write your answer choices in the spaces where they belong. You can either write the letter of your answer choice or you can copy the sentence.

Teotihuacán was a highly developed city in Mesoamerica that reached its peak between about 150 and 700.

Answer Choices

A The number and sophistication of the architectural, administrative,mercial, and religious features of Teotihuacán indicate the existence of centralized planning and control.

B Teotihuacán may have developed its own specific local religion as a result of the cultural advances made possible by the city’s great prosperity.

C Several factors may account for Teotihuacán’s extraordinary development, including its location, rich natural resources, irrigation potential, intelligent elite, and the misfortune of rivalmunities.

D As a result of its large number of religious shrines, by the first century , Teotihuacán became the most influential religious center in all of Mesoamerica.

E In many important areas, from the obsidian industry to religious tourism, Teotihuacán’s success and prosperity typified the classic positive feedback cycle.

F Although many immigrants settled in Teotihuacán between 150 and 700, the increasing threat of coerced labor discouraged further settlement and limited Teotihuacán’s population growth.

1. B

2. D

3. C

4. D

5. A