TPO42阅读文本及答案解析

Explaining Dinosaur Extinction

Dinosaurs rapidly became extinct about 65 million years ago as partof a mass extinction known as the K-T event, because it is associated with ageological signature known as the K-T boundary, usually a thin band ofsedimentation found in various parts of the world (K is the traditional abbreviationfor the Cretaceous, derived from the German name Kreidezeit). Many explanationshave been proposed for why dinosaurs became extinct. For example, some haveblamed dinosaur extinction on the development of flowering plants, which weresupposedly more difficult to digest and could have caused constipation orindigestion—except that flowering plants first evolved in the Early Cretaceous,about 60 million years before the dinosaurs died out. In fact, severalscientists have suggested that the duckbill dinosaurs and homed dinosaurs, withtheir complex battery of grinding teeth, evolved to exploit this new resourceof rapidly growing flowering plants Others have blamed extinction oncompetition from the mammals, which allegedly ate all the dinosaur eggs—exceptthat mammals and dinosaurs appeared at the same time in the Late Triassic,about 190 million years ago, and there is no reason to believe that mammalssuddenly acquired a taste for dinosaur eggs after 120 million years ofcoexistence Some explanations (such as the one stating that dinosaurs all diedof diseases) fail because there is no way to scientifically test them, and theycannot move beyond the realm of speculation and guesswork.

This focus on explaining dinosaur extinction misses an importantpoint the extinction at the end of the Cretaceous was a global event thatkilled off organisms up and down the food chain. It wiped out many kinds ofplankton in the ocean and many marine organisms that lived on the plankton atthe base of the food chain. These included a variety of clams and snails, andespecially the ammonites, a group of shelled squidlike creatures that dominatedthe Mesozoic seas and had survived many previous mass extinctions. The K-Tevent marked the end of the marine reptiles, such as the mosasaurs and theplesiosaurs, which were the largest creatures that had ever lived in the seasand which ruled the seas long before whales evolved. On land, there was also acrisis among the land plants, in addition to the disappearance of dinosaurs. Soany event that can explain the destruction of the base of the food chain(plankton in the ocean, plants on land) can better explain what happened toorganisms at the top of the food chain, such as the dinosaurs. By contrast, anyexplanation that focuses strictly on the dinosaurs completely misses the pointThe Cretaceous extinctions were a global phenomenon, and dinosaurs were just apart of a bigger picture.

According to one theory, the Age of Dinosaurs ended suddenly 65million years ago when a giant rock from space plummeted to Earth. Estimated tobe ten to fifteen kilometers in diameter, this bolide (either a comet or anasteroid) was traveling at cosmic speeds of 20-70 kilometers per second, or45,000-156,000 miles per hour. Such a huge mass traveling at such tremendousspeeds carries an enormous amount of energy. When the bolide struck this energywas released and generated a huge shock wave that leveled everything forthousands of kilometers around the impact and caused most of the landscape toburst into flames. The bolide struck an area of the Yucatan Peninsula of Mexicoknown as Chicxulub, excavating a crater 15-20 kilometers deep and at least 170kilometers in diameter. The impact displaced huge volumes of seawater, causingmuch flood damage in the Caribbean. Meanwhile, the bolide itself excavated 100cubic kilometers of rock and debris from the site, which rose to an altitude of100 kilometers. Most of it fell back immediately, but some of it remained asdust in the atmosphere for months. This material, along with the smoke from thefires, shrouded Earth, creating a form of nuclear winter. According tocomputerized climate models, global temperatures fell to near the freezingpoint, photosynthesis halted, and most plants on land and in the sea died. Withthe bottom of the food chain destroyed, dinosaurs could not survive.

paragraph 1

Dinosaurs rapidly became extinct about 65 million years ago as partof a mass extinction known as the K-T event, because it is associated with ageological signature known as the K-T boundary, usually a thin band ofsedimentation found in various parts of the world (K is the traditionalabbreviation for the Cretaceous, derived from the German name Kreidezeit). Manyexplanations have been proposed for why dinosaurs became extinct. For example,some have blamed dinosaur extinction on the development of flowering plants,which were supposedly more difficult to digest and could have causedconstipation or indigestion—except that flowering plants first evolved in theEarly Cretaceous, about 60 million years before the dinosaurs died out. Infact, several scientists have suggested that the duckbill dinosaurs and homeddinosaurs, with their complex battery of grinding teeth, evolved to exploitthis new resource of rapidly growing flowering plants Others have blamedextinction on competition from the mammals, which allegedly ate all thedinosaur eggs—except that mammals and dinosaurs appeared at the same time inthe Late Triassic, about 190 million years ago, and there is no reason tobelieve that mammals suddenly acquired a taste for dinosaur eggs after 120million years of coexistence Some explanations (such as the one stating thatdinosaurs all died of diseases) fail because there is no way to scientificallytest them, and they cannot move beyond the realm of speculation and guesswork.

In paragraph 1, why does the author include a discussion of whenflowering plants evolved?

To help explain why some scientists believe that the development offlowering plants led to dinosaur extinction

To cast doubt on the theory that the development of flowering plantscaused dinosaurs to become extinct

To suggest that dinosaurs were able to survive for as long as theydid because of the availability of flowering plants

To emphasize that duckbill dinosaurs and horned dinosaurs were thefirst dinosaurs to become extinct

The word “allegedly” in the passage is closest in meaning to

inevitably

gradually

Supposedly

Increasingly

3. According to paragraph 1 the extinction of the dinosaurs isunlikely to have been the result of competition from mammals because

A. mammals would not have been capable of eating dinosaur eggs

B. mammals did not appear in any significant numbers until after theLate Triassic

C. mammals and dinosaurs did not, in fact, compete for any of thesame resources

D. mammals and dinosaurs lived together for roughly 120 millionyears before the extinction

paragraph 2

This focus on explaining dinosaur extinction misses an importantpoint the extinction at the end of the Cretaceous was a global event thatkilled off organisms up and down the food chain. It wiped out many kinds ofplankton in the ocean and many marine organisms that lived on the plankton atthe base of the food chain. These included a variety of clams and snails, andespecially the ammonites, a group of shelled squidlike creatures that dominatedthe Mesozoic seas and had survived many previous mass extinctions. The K-Tevent marked the end of the marine reptiles, such as the mosasaurs and theplesiosaurs, which were the largest creatures that had ever lived in the seasand which ruled the seas long before whales evolved. On land, there was also a crisisamong the land plants, in addition to the disappearance of dinosaurs. So anyevent that can explain the destruction of the base of the food chain (planktonin the ocean, plants on land) can better explain what happened to organisms atthe top of the food chain, such as the dinosaurs. By contrast, any explanationthat focuses strictly on the dinosaurs completely misses the point The Cretaceousextinctions were a global phenomenon, and dinosaurs were just a part of abigger picture.

paragraph 3

According to one theory, the Age of Dinosaurs ended suddenly 65million years ago when a giant rock from space plummeted to Earth. Estimated tobe ten to fifteen kilometers in diameter, this bolide (either a comet or anasteroid) was traveling at cosmic speeds of 20-70 kilometers per second, or45,000-156,000 miles per hour. Such a huge mass traveling at such tremendousspeeds carries an enormous amount of energy. When the bolide struck this energywas released and generated a huge shock wave that leveled everything forthousands of kilometers around the impact and caused most of the landscape toburst into flames. The bolide struck an area of the Yucatan Peninsula of Mexicoknown as Chicxulub, excavating a crater 15-20 kilometers deep and at least 170kilometers in diameter. The impact displaced huge volumes of seawater, causingmuch flood damage in the Caribbean. Meanwhile, the bolide itself excavated 100cubic kilometers of rock and debris from the site, which rose to an altitude of100 kilometers. Most of it fell back immediately, but some of it remained asdust in the atmosphere for months. This material, along with the smoke from thefires, shrouded Earth, creating a form of nuclear winter. According tocomputerized climate models, global temperatures fell to near the freezingpoint, photosynthesis halted, and most plants on land and in the sea died. Withthe bottom of the food chain destroyed, dinosaurs could not survive.

4. According to paragraph 2, what is problematic about somescientists' focus on dinosaur extinction?

A. Dinosaurs became extinct so long ago that no theory about theirdisappearance can be proven scientifically.

B. Dinosaurs were not the only organisms that went extinct at theend of the Cretaceous period.

C. More marine organisms went extinct during the Cretaceous than diddinosaur species.

D. It is more important to understand how plankton and other marineorganisms came to thrive during the Cretaceous period.

5. According to paragraph 2, each of the following became extinctduring the K-T event EXCEPT

A. early species of whales

B. marine reptiles

C. various species of clams

D. many species of land plants

6. What makes the extinction of “the ammonites” especiallysignificant?

A. They were among the largest creatures that ever lived.

B. They existed at the lowest level of the food chain.

C. They had been able to survive in the Mesozoic seas.

D. They had survived many previous mass extinctions.

7. The word “halted” in the passage is closest in meaning to

A. slowed

B. stopped

C. contracted

D. declined

8. The word “strictly" in the passage is closest in meaning to

A. exclusively

B. mainly

C. initially

D. Wrongly

9. The word “crisis” in the passage is closest in meaning to

A. collapse

B. disturbance

C. critical situation

D. loss

10. How does paragraph 3 relate to paragraph 2?

A. Paragraph 3 provides an alternative explanation to the oneprovided in paragraph 2.

B. Paragraph 3 provides an explanation that satisfies the conditionsset forth in paragraph 2.

C. Paragraph 3 provides the facts to support the theory presented inparagraph 2.

D. Paragraph 3 presents a theory that calls into question theposition described in paragraph 2.

paragraph 3

According to one theory, the Age of Dinosaurs ended suddenly 65million years ago when a giant rock from space plummeted to Earth. Estimated tobe ten to fifteen kilometers in diameter, this bolide (either a comet or anasteroid) was traveling at cosmic speeds of 20-70 kilometers per second, or45,000-156,000 miles per hour. Such a huge mass traveling at such tremendousspeeds carries an enormous amount of energy. When the bolide struck this energywas released and generated a huge shock wave that leveled everything forthousands of kilometers around the impact and caused most of the landscape toburst into flames. The bolide struck an area of the Yucatan Peninsula of Mexicoknown as Chicxulub, excavating a crater 15-20 kilometers deep and at least 170kilometers in diameter. The impact displaced huge volumes of seawater, causingmuch flood damage in the Caribbean. Meanwhile, the bolide itself excavated 100cubic kilometers of rock and debris from the site, which rose to an altitude of100 kilometers. Most of it fell back immediately, but some of it remained asdust in the atmosphere for months. This material, along with the smoke from thefires, shrouded Earth, creating a form of nuclear winter. According tocomputerized climate models, global temperatures fell to near the freezingpoint, photosynthesis halted, and most plants on land and in the sea died. Withthe bottom of the food chain destroyed, dinosaurs could not survive.

11. Paragraph 3 answers all of the following questions EXCEPT:

A. Why did the bolide fall to Earth?

B. How fast was the bolide traveling?

C. How was the bolide capable of generating a shock wave?

D. How did the bolide cause flood damage to the Caribbean?

12. Paragraph 3 strongly suggests that if the bolide impact theoryis correct, the majority of the extinctions associated with the K-T eventresulted from

A. sunlight being blocked for months by dust and smoke in Earth'satmosphere

B. widespread flooding that followed the displacement of hugevolumes of seawater

C. the leveling of the landscape by the shock wave that wasgenerated when the bolide struck Earth

D. the rise in global temperatures caused by the fires that burnedmuch of the landscape

13. Look at the four squares [■] that indicate where the following sentence could be added to thepassage.

Some explanations seem plausible until the facts are considered.

Where would the sentence best fit? Click on a square [■] to add the sentence to thepassage.

Dinosaurs rapidly became extinct about 65 million years ago as partof a mass extinction known as the K-T event, because it is associated with ageological signature known as the K-T boundary, usually a thin band ofsedimentation found in various parts of the world (K is the traditionalabbreviation for the Cretaceous, derived from the German name Kreidezeit). [■] Many explanations have beenproposed for why dinosaurs became extinct. [■] For example, some have blamed dinosaur extinction on thedevelopment of flowering plants, which were supposedly more difficult to digestand could have caused constipation or indigestion—except that flowering plantsfirst evolved in the Early Cretaceous, about 60 million years before thedinosaurs died out. [■]In fact, several scientists have suggested that the duckbilldinosaurs and homed dinosaurs, with their complex battery of grinding teeth,evolved to exploit this new resource of rapidly growing flowering plants. [■]Others have blamed extinction oncompetition from the mammals, which allegedly ate all the dinosaur eggs—exceptthat mammals and dinosaurs appeared at the same time in the Late Triassic,about 190 million years ago, and there is no reason to believe that mammalssuddenly acquired a taste for dinosaur eggs after 120 million years ofcoexistence Some explanations (such as the one stating that dinosaurs all diedof diseases) fail because there is no way to scientifically test them, and theycannot move beyond the realm of speculation and guesswork.

14. Direction: An introductory sentence for a brief summary of thepassage is provided below. Complete the summary by selecting the THREE answerchoices that express the important ideas in the passage. Some sentences do notbelong in the summary because they express ideas that are not presented in thepassage or are minor ideas in the passage. This question is worth 2 points.

Drag your answer choices to the spaces where they belong. To removean answer choice, click on it.

To review the passage, click VIEW TEXT.

Over the years, scientists have proposed a number of theories as towhy dinosaurs suddenly became extinct about 65 million years ago.

Answer Choices

Many explanations for dinosaur extinction have been proposed, butmost of them are either called into question by known facts or are merelyunsupported hypotheses.

Focusing on dinosaurs misses the point that the extinction, at aboutthe same time, of the shelled squidlike creatures that dominated the Mesozoicseas was far more scientifically significant.

Computerized climate models of global temperature fluctuationssupport the theory that a huge rock from space hit the Yucatan Peninsula inMexico about 65 million years ago.

Although mammals and dinosaurs appeared at about the same time inthe Late Triassic, the K-T event, which marked the end of the dinosaurs,apparently had relatively little impact on mammals.

Any satisfactory explanation of the mass extinction of dinosaursmust take into account the fact that the disappearance of the dinosaurs waspart of a global mass extinction.

A huge bolide striking Earth would have created conditions in whichmost plants would have died, thus explaining the mass extinction oforganisms—including dinosaurs—further up the food chain.