托福阅读TPO33(试题+答案+翻译)第3篇:灭绝事件
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托福阅读TPO33阅读原文
Extinction Episodes of the Past
【1】It was not until the Cambrian period, beginning about 600 million years ago, that a great proliferation of macroscopic species occurred on Earth and produced a fossil record that allows us to track the rise and fall of biodiversity. Since the Cambrian period, biodiversity has generally risen, but there have been some notable exceptions. Biodiversity collapsed dramatically during at least five periods because of mass extinctions around the globe. The five major mass extinctions receive most of the attention, but they are only one end of a spectrum of extinction events. Collectively, more species went extinct during smaller events that were less dramatic but more frequent. The best known of the five major extinction events, the one that saw the demise of the dinosaurs, is the Cretaceous-Tertiary extinction.
【2】Starting about 280 million years ago, reptiles were the dominant large animals in terrestrial environments. In popular language this was the era “when dinosaurs ruled Earth,” when a wide variety of reptile species occupying many ecological niches. However, no group or species can maintain its dominance indefinitely, and when, after over 200 million years, the age of dinosaurs came to a dramatic end about 65 million years ago, mammals began to flourish, evolving from relatively few types of small terrestrial animals into the myriad of diverse species, including bats and whales, that we know today. Paleontologists label this point in Earth’s history as the end of the Cretaceous period and the beginning of the Tertiary period, often abbreviated as the K-T boundary. This time was also marked by changes in many other types of organisms. Overall, about 38 percent of the families of marine animals were lost, with percentages much higher in some groups Ammonoid mollusks went from being very diverse and abundant to being extinct. An extremely abundant set of planktonic marine animals called foraminifera largely disappeared, although they rebounded later. Among plants, the K-T boundary saw a sharp but brief rise in the abundance of primitive vascular plants such as ferns, club mosses, horsetails, and conifers and other gymnosperms. The number of flowering plants (angiosperms) was reduced at this time, but they then began to increase dramatically.
【3】What caused these changes? For many years scientists assumed that a cooling of the climate was responsible, with dinosaurs being particularly vulnerable because, like modern reptiles, they were ectothermic (dependent on environmental heat, or cold-blooded). It is now widely believed that at least some species of dinosaurs had a metabolic rate high enough for them to be endotherms (animals that maintain a relatively consistent body temperature by generating heat internally). Nevertheless, climatic explanations for the K-T extinction are not really challenged by the ideas that dinosaurs may have been endothermic, because even endotherms can be affected by a significant change in the climate.
【4】Explanations for the K-T extinction were revolutionized in 1980 when a group of physical scientists led by Luis Alvarez proposed that 65 million years ago Earth was stuck by a 10-kilometer-wide meteorite traveling at 90,000 kilometers per hour. They believed that this impact generated a thick cloud of dust that enveloped Earth, shutting out much of the incoming solar radiation and reducing plant photosynthesis to very low levels. Short-term effects might have included huge tidal waves and extensive fires. In other words, a series of events arising from a single cataclysmic event caused the massive extinctions. Initially, the meteorite theory was based on a single line of evidence. At locations around the globe, geologists had found an unusually high concentration of iridium in the layer of sedimentary rocks that was formed about 65 million years ago. Iridium is an element that is usually uncommon near Earth’s surface, but it is abundant in some meteorites. Therefore, Alvarez and his colleagues concludedthat it was likely that the iridium in sedimentary rocks deposited at the K-T boundary had originated in a giant meteorite or asteroid. Most scientist came to accept the meteorite theory after evidence came to light that a circular formation, 180 kilometers in diameter in diameter and centered on the north coast of the Yucatan Peninsula, was created by a meteorite impact about 65 million years ago.
托福阅读TPO33阅读试题
1.The word "proliferation" in the passage (paragraph 1) is closest in meaning to
A.decline.
B.extinction.
C.increase.
D.migration.
2.Paragraph 1 supports which of the following statements about life on Earth before the Cambrian period?
A.Biodiversity levels were steady, as indicated by the fossil record.
B.Levels of biodiversity could not be tracked.
C.The most dramatic extinction episode occurred.
D.Few microscopic species existed.
3.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.The dominance of dinosaurs came to an end 65 million years ago, at which time mammals began to flourish and diversify.
B.Because no group of species can remain dominant forever, mammals became the dominant group when dinosaurs became extinct.
C.After being the dominant group for more than 200 million years, the age of dinosaurs came to a dramatic end 65 million years ago.
D.The diverse group of mammals that we know today, including bats and whales, evolved from small terrestrial forms that had been dominated by dinosaurs.
4.According to paragraph 2, why are dinosaurs popularly said to have "ruled Earth" during the Cretaceous period?
A.Dinosaurs were the only species of reptile that existed during the whole of the Cretaceous period.
B.Dinosaurs won the battle for food resources over mammals during the Cretaceous period.
C.Dinosaurs survived extinction during the Cretaceous period, whereas many other animal species did not.
D.Dinosaurs were the physically and ecologically dominant animals during the Cretaceous period.
5.According to paragraph 2, which of the following species initially increased in number at the K-T boundary?
A.Dinosaurs.
B.Foraminifera.
C.Ferns.
D.Ammonoid mollusks.
6.Why does the author note that "even endotherms can be affected by a significant change in the climate"(paragraph 3)?
A.To argue that there was a significant climate at the time that endothermic dinosaurs became extinct.
B.To argue that climate change caused some dinosaurs to evolve as endotherms.
C.To support the view that at least some of the dinosaurs that became extinct were endotherms.
D.To defend climate change as possible explanation for the extinction of dinosaurs.
7.The word "generated"(paragraph 4) in the passage is closest in meaning to
A.collected.
B.produced.
C.spread.
D.added.
8.The word "extensive"(paragraph 4) in the passage is closest in meaning to
A.widespread.
B.sudden.
C.numerous.
D.subsequent.
9.According to paragraph 4, all of the following contributed to the massive extinctions of the K-T period EXCEPT:
A.tidal waves.
B.fires.
C.insufficient solar radiation.
D.iridium.
10.According to paragraph 4, which of the following statements explains the importance of the discovery of high levels of iridium rocks?
A.It provided evidence that overexposure to solar radiation led to the K-T extinction.
B.It showed that more than one cataclysmic event was responsible for the K-T extinction.
C.It suggested that the cause of the K-T extinction may have been a meteorite striking Earth.
D.It provided evidence that the K-T extinction occurred 65 million years ago.
11.According to paragraph 4, which of the following is true about the Yucatan Peninsula?
A.The circular formation there was caused by a meteorite impact 65 million years ago.
B.Sedimentary rocks from that area have the lowest iridium concentration of any rocks on Earth.
C.There is evidence that a huge tidal wave occurred there 65 million years ago.
D.Evidence found there challenged the meteorite impact theory.
12.Which of the following can be inferred from paragraph 4 about the meteorite theory?
A.The data originally presented as evidence for the theory were eventually rejected.
B.Many scientists did not accept it when it was first proposed.
C.It has not been widely accepted as an explanation for the K-T extinction.
D.Alvarez subsequently revised it after a circular formation was found in the Yucatan Peninsula.
13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit? This focused on the chemical composition of ancient rocks.
Explanations for the K-T extinction were revolutionized in 1980 when a group of physical scientists led by Luis Alvarez proposed that 65 million years ago Earth was stuck by a 10-kilometer-wide meteorite traveling at 90,000 kilometers per hour. They believed that this impact generated a thick cloud of dust that enveloped Earth, shutting out much of the incoming solar radiation and reducing plant photosynthesis to very low levels. Short-term effects might have included huge tidal waves and extensive fires. In other words, a series of events arising from a single cataclysmic event caused the massive extinctions. ■【A】Initially, the meteorite theory was based on a single line of evidence. ■【B】At locations around the globe, geologists had found an unusually high concentration of iridium in the layer of sedimentary rocks that was formed about 65 million years ago. ■【C】Iridium is an element that is usually uncommon near Earth's surface, but it is abundant in some meteorites. ■【D】Therefore, Alvarez and his colleagues concluded that it was likely that the iridium in sedimentary rocks deposited at the K-T boundary had originated in a giant meteorite or asteroid. Most scientist came to accept the meteorite theory after evidence came to light that a circular formation, 180 kilometers in diameter in diameter and centered on the north coast of the Yucatan Peninsula, was created by a meteorite impact about 65 million years ago.
14. Prose Summary
The K-T extinction 65 million years ago is the best known of the five major extinction episodes since the Cambrian period.
A.Collectively, the five major extinction episodes resulted in the elimination of a larger number of species than did all the minor extinction events.
B.The K-T extinction eliminated the dinosaurs and ammonoid mollusks but was followed by the diversification of mammals and gymnospermous plants.
C.An extreme cooling of the climate could not have caused the K-T extinction of dinosaurs, because, while most dinosaurs depended on environmental heat, some did not.
D.The K-T extinction of the dinosaurs is the only mass extinction that has been explained by the impact of a meteorite.
E.In 1980 Luis Alvarez proposed that the K-T extinction was caused by ecological disasters brought about by the impact of a meteorite striking Earth.
F.A high concentration of iridium in sedimentary rocks at the K-T boundary and a large impact crater in the Yucatan Peninsula from 65 million years ago strongly support Alvarez' hypothesis.
托福阅读TPO33阅读答案
1.proliferation，繁殖，激增，对应C。
2.推断题：定位句It was not until the Cambrian period, beginning about 600 million years ago, that a great proliferation of macroscopic species occurred on Earth and produced a fossil record that allows us to track the rise and fall of biodiversity.主要意思是直到寒武纪才能够监测生物多样性。言外之意就是在寒武纪之前就不能监测生物多样性，对应B选项。
3.解析句子简化题：该长句其实是2个长句的并列;主要分成2个意思：第一是没有任何一种生物能永远地统治，第二是恐龙灭亡之后，哺乳动物开始发展统治，且两层意思之间可以构成因果关系。所以只有B选项满足所有条件。
4.解析细节题：定位句Starting about 280 million years ago, reptiles were the dominant large animals in terrestrial environments. In popular language this was the era "when dinosaurs ruled Earth," when a wide variety of reptile species occupying many ecological niches.对应D选项。
5.解析细节题：定位句Paleontologists label this point in Earth's history as the end of the Cretaceous period and the beginning of the Tertiary period，often abbreviated as the K-T boundary. This time was also marked by changes in many other types of organisms. Overall, about 38 percent of the families of marine animals were lost, with percentages much higher in some groups
Ammonoid mollusks went from being very diverse and abundant to being extinct.题干中的范围限定initially，因此只可能是Ammonoid mollusk.选D。
6.解析修辞目的题：题干中的even甚至，表示程度的递进。定位句Nevertheless, climatic explanations for the L-T extinction are not really challenged by the ideas that dinosaurs may have been endothermic。即后半句的原因解释了气候理论为什么不被反驳。
7.generate，产生，选B。
8.extensive，广泛的，选A。
9.解析否定细节题：定位句 Short-term effects might have included huge tidal waves and extensive fires. In other words, a series of events arising from a single cataclysmic event caused the massive extinctions.对应A选项，B选项。定位句 They believed that its impact generated a thick cloud of dust that enveloped Earth, shutting out much of the incoming solar radiation and reducing plant photosynthesis to very low levels.意思是这种冲击产生了大量的厚尘云，遮蔽了天空和阳光。对应C选项。而D选项，iridium是有关灭绝的证据，但并非构成灭绝的原因。
10.解析细节题：定位句Initially, the meteorite theory was based on a single line of evidence. At locations around the globe, geologists have found an unusually high concentration of iridium in the layer of sedimentary rocks that was formed about 65 million years ago.意思是说小行星撞击理论一开始主要的证据就 是在地球的岩石中发现了大量的iridium (铱)。因此其重要性就是说明该撞击理论是物种大灭绝的原因。
11.解析细节题：定位句Most scientists came to accept the meteorite theory after evidence came to light that a circular formation, 180 kilometers in diameter and centered on the north coast of the Yucatan Peninsula, was created by a meteorite impact about 65 million years ago.意思是说在Yucatan Peninsula背岸的大坑是陨石撞击的结果。对应A选项。
12.解析推断题：定位句 Initially, the meteorite theory was based on a single line of evidence. 一开始仅依赖于单一证据的理论，暗示了证据还不够充分。定位句 Most scientists came to accept the meteorite theory after evidence came to light that a circular formation，180 kilometers in diameter and centered on the north coast of the Yucatan Peninsula, was created by a meteorite impact about 65 million years ago.在环形坑证据出现之后大多数的科学家才开始接受小 行星撞击理论，就是说一开始大多数科学家对该理论是持有怀疑态度的。即答案就是B。
13.解析句子插入题：给出的句子中出现了this的指代提示，表示前面的内容可能 与石头的化学组成无关，而该句的下一句应该与化学组成有关。因此只有 第二个方框满足条件。在第二个方框之后才出现了对于iridium的讨论。
14.The K-T extinction eliminated the dinosaurs and ammonoid mollusks but was followed by the diversification of mammals and gymnospermous plants.正确。对应第二段段落大意，没有永生的统治者，恐龙之后现在是哺乳动物和植物的天下。
In 1980 Luis Alvarez proposed that the K-T extinction was caused by ecological disasters brought about by the impact of a meteorite striking Earth.正确。对应第四段主旨：小行星撞击地球假说。
A high concentration of iridium in sedimentary rocks at the K-T boundary and a large impact crater in the Yucatan Peninsula from 65 million years ago strongly support Alvarez, hypothesis.正确。对应第四段解释小行星撞击地球假说的重要证据。一个证据是Iridium在 地球岩石中的大量出现，另一个证据是巨大环形坑的发现。
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