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[雅思机经]2016年10月13日雅思阅读真题回顾

来源:网络 2016-10-20 编辑:朗阁小编 雅思托福0元试学

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朗阁海外考试研究中心的雅思培训老师为考生带来2016年10月13日的真题回顾、详细解析及备考策略,此为雅思阅读回顾部分。

朗阁海外考试研究中心   辛晓庆

朗阁海外考试研究中心的雅思培训为考生带来2016年10月13日的真题回顾、详细解析及备考策略,此为雅思阅读回顾部分。

 

考试日期

20161013

 

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Reading Passage 1

Title:

The Dinosaurs Footprints and Extinction (2012.11.03 P1)

Question types

判断题 (6)

填空式Summary (7)

相关英文原文阅读

The Dinosaurs Footprints and Extinction

Cases in which many species become extinct within a geologically short interval of time are called mass extinctions. There was one such event at the end of the Cretaceous period (around 70 million years ago). There was another, even larger, mass extinction at the end of the Permian period (around 250 million years ago). The Permian event has attracted much less attention than other mass extinctions because mostly unfamiliar species perished at that time.

 

The fossil record shows at least five mass extinctions in which many families of marine organisms died out. The rates of extinction happening today are as great as the rates during these mass extinctions. Many scientists have therefore concluded that a sixth great mass extinction is currently in progress.

 

What could cause such high rates of extinction? There are several hypotheses, including warming or cooling of Earth, changes in seasonal fluctuations or ocean currents, and changing positions of the continents. Biological hypotheses include ecological changes brought about by the evolution of cooperation between insects and flowering plants or of bottom feeding predators in the oceans. Some of the proposed mechanisms required a very brief period during which all extinctions suddenly took place; other mechanisms would be more likely to have taken place more gradually, over an extended period, or at different times on different continents.

 

Some hypotheses fail to account for simultaneous extinctions on land and in the seas. Each mass extinction may have had a different cause. Evidence points to hunting by humans and habitat destruction as the likely causes for the current mass extinction.

 

American paleontologists David Raup and John Sepkoski, who have studied extinction rates in a number of fossil groups, suggest that episodes of increased extinction have recurred periodically, approximately every 26 million years since the mid Cretaceous period. The late Cretaceous extinction of the dinosaurs and am-monoids was just one of the more drastic in a whole series of such recurrent extinction episodes. The possibility that mass extinctions may recur periodically has given rise to such hypotheses as that of a companion star with a long period orbit deflecting other bodies from their normal orbits, making some of them fall to Earth as meteors and causing widespread devastation upon impact.

 

Of the various hypotheses attempting to account for the late Cretaceous extinctions, the one that has attracted the most attention in recent years is the asteroid impact hypothesis first suggested by Luis and Walter Alvarez. According to this hypothesis, Earth collided with an asteroid with an estimated diameter of 10 kilometers, or with several asteroids, the combined mass of which was comparable. The force of collision spewed large amounts of debris into the atmosphere, darkening the skies for several years before the finer particles settled. The reduced level of photosynthesis led to a massive decline in plant life of all kinds, and this caused massive starvation first of herbivores and subsequently of carnivores.

 

The mass extinction would have occurred very suddenly under this hypothesis. One interesting test of the Alvarez hypothesis is based on the presence of the rare-earth element iridium (Ir). Earth's crust contains very little of this element, but most asteroids contain a lot more. Debris thrown into the atmosphere by an asteroid collision would presumably contain large amounts of iridium, and atmospheric currents would carry this material all over the globe. A search of sedimentary deposits that span the boundary between the Cretaceous and Tertiary periods shows that there is a dramatic increase in the abundance of iridium briefly and precisely at this boundary. This iridium anomaly offers strong support for the Alvarez hypothesis even though no asteroid itself has ever been recovered.

 

An asteroid of this size would be expected to leave an immense crater, even if the asteroid itself was disintegrated by the impact. The intense heat of the impact would produce heat shocked quartz in many types of rock. Also, large blocks thrown aside by the impact would form secondary craters surrounding the main crater. To date, several such secondary craters have been found along Mexico's Yucatan Peninsula, and heat shocked quartz has been found both in Mexico and in Haiti. A location called Chicxulub, along the Yucatan coast, has been suggested as the primary impact site.

题型难度分析

本篇文章整体难度适中,题型中规中矩,部分词汇科学性较强,比如meteorite, asteroid等。建议考生在复习备考过程中,扩大涉猎面,可以定期的去新科学家(New Scientist)和科学美国人(Scientific American)官网上选择感兴趣的文章进行阅读,扩大自己的知识面。

题型技巧分析

一般如果文章中没有考小标题题和搭配题,那么这篇文章通常有全文顺序性。本篇文章是典型的全文顺序性,根据两种题型的内部顺序性,按部就班得选词定位解题即可。但是烤鸭们在解题过程中需要注意的是一定要养成先看文章标题确定文章主旨词的习惯。主旨词一旦确定,在选词定位过程中需要绕开文章主旨词。

另外,在雅思和托福阅读中,都考过关于恐龙灭绝的文章,这种文章一般的行文结构都是现象解释,提出三到四个hypothesis, 按照套路,一般都是较后一个假说较合理,其他的前面提到的假说都会被否定。综合雅思和托福阅读,恐龙灭绝的原因理论较为广泛接受的一个假说就是asteroid impact theory(小行星撞击地球理论)了。