托福TPO33阅读Passage3原文文本+题目+答案解析.pdf
《托福TPO33阅读Passage3原文文本+题目+答案解析.pdf》由会员分享,可在线阅读,更多相关《托福TPO33阅读Passage3原文文本+题目+答案解析.pdf(8页珍藏版)》请在三一文库上搜索。
1、 为了帮助大家高效备考托福, 为大家带来托福 TPO33 阅读 Passage3 原文文本+题目+答案 解析,希望对大家备考有所帮助。 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 t
2、he 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 at
3、tention,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 extin
4、ction. 【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 do
5、minance 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.
6、Paleontologists label this point in Earths 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
7、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 bri
8、ef 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 assum
9、ed 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 the
10、m 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 sign
11、ificant 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 thi
12、s 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 cat
13、aclysmic 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
14、 element that is usually uncommon near Earths 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 acce
15、pt 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. 1.The word“proliferation“in the passage(paragraph 1)is closest
16、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 dram
17、atic 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 dinosa
18、urs 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 dinosa
19、urs 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 Cretaceou
20、s 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 n
21、ot. 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“
22、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 lea
23、st 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
24、 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,whic
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 托福 TPO33 阅读 Passage3 原文 文本 题目 答案 解析
链接地址:https://www.31doc.com/p-3368535.html