亲爱的同学们，在做TPO阅读的时候，你是否被大量生词搞得晕头转向？很多学生初学托福[微博]阅读，看到不认识的单词会一个一个查字典，特别浪费时间。很多同学因为不耐烦查单词，放弃或者延误了托福学习。现在，为了节省大家的时间，笔者为大家整理了TPO上的重点单词。学学这些单词吧！TOEFL之TPO阅读单词语境记忆，让记忆单词快速准确！

　　新托福之TPO阅读重点单词语境记忆41

Mass Extinctions

　　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 ammonoids 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。

　　托福核心单词

　　Cretaceous 白垩纪；白垩纪的

　　原文：There was one such event at the end of the Cretaceous period (around 70 million years ago). 在白垩纪时期后期(大约七千万年前)就曾经发生过一次大规模物种灭绝。

　　强化记忆：The Cretaceous extinction was like a terrible streak of bad luck lasting millions of years. 白垩纪的生物绝灭，犹如一场持续千百万年的可怕厄运。

　　The story takes place 6500 years ago in the Cretaceous period. 故事发生在6500万年前的白垩纪晚期。

　　Permian 二叠纪

　　原文：There was another, even larger, mass extinction at the end of the Permian period (around 250 million years ago)。在二叠纪时期后期(大约两亿五千万年前)还发生过一次规模更大的物种灭绝。

　　强化记忆：Permian peak here range upon range of hills. 这里层峦叠峰。

　　The Permian system has the extensive distribution in these basins. 二叠系在这些盆地有着广泛的分布。

　　Perish 毁坏，死亡

　　原文：The Permian event has attracted much less attention than other mass extinctions because mostly unfamiliar species perished at that time。由于当时灭绝的物种很少为人类所知，所以二叠纪时期的大规模物种灭绝受到的关注远远不如其他几次大规模物种灭绝。

　　强化记忆：Crowns and thrones may perish. 王权不会永存。

　　Most of the butterflies perish in the first frosts of autumn. 大多数蝴蝶会在秋天的第一场霜冻来临时纷纷死去。

　　Hypothesis 假设

　　原文：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. 根据这一假说，地球与一个直径约为10公里的小行星或者总体积与之相当的几个小行星发生碰撞。

　　强化记忆：We have proved the hypothesis. 我们已经证明了这种假设。

　　The new discoveries have falsified that hypothesis. 新的发现已证明那个假定是无根据的。

　　Predator食肉动物，捕食者

　　原文：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. 生物假说包括因昆虫与开花植物之间的合作式进化或海洋底层肉食动物进化引起的生态变化。

　　强化记忆： the relationship between predator and prey. 捕食性动物与猎物之间的关系

　　The terror bird was the top predator in its ancestral home. 恐鸟是其远古家园中的顶级捕食者。

　　Paleontologists 古生物学者

　　原文：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. 美国古生物学家David Raup 和 John Sepkoski 曾经从大量化石群中研究物种灭绝的比率。他们指出，自从白垩纪时期中期以来，灭绝的物种不断增多，大约每隔两千六百万年就会定期发生一次。

　　强化记忆：Paleontologists also debated whether Archaeopteryx could fly. 古生物学家还讨论了始祖鸟是否会飞的问题。

　　Paleontologists digging in Oklahoma have uncovered bones from the tallest dinosaur ever. 古生物学家在俄克拉何马州发掘出了迄今为止个头最高的恐龙化石。

　　Episode 插曲，一段情节

　　原文：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. 美国古生物学家David Raup 和 John Sepkoski 曾经从大量化石群中研究物种灭绝的比率。他们指出，自从白垩纪时期中期以来，灭绝的物种不断增多，大约每隔两千六百万年就会定期发生一次。

　　强化记忆： I'd like to try and forget the whole episode. 我倒想尽量把那段经历全部忘掉。

　　The episode was a huge embarrassment for all concerned. 这段小插曲令所有有关人员都感到非常尴尬。

　　Orbit 轨道，生活常规

　　原文：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。对于周期性出现大规模物种灭绝的可能性，引发了这样的假设：一颗具有长周期轨道的伴星体使其他天体从正常轨道偏离，导致其中一些天体变成流星掉落到地球，撞击时造成大范围破坏。

　　强化记忆：The space rocket was launched and went into orbit. 宇宙火箭发射后进入轨道。

　　The satellite was launched into orbit around the moon. 卫星被射入环绕月球的轨道。

　　Deflect 使偏斜，转向

　　原文：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。对于周期性出现大规模物种灭绝的可能性，引发了这样的假设：一颗具有长周期轨道的伴星体使其他天体从正常轨道偏离，导致其中一些天体变成流星掉落到地球，撞击时造成大范围破坏。

　　强化记忆：Never let a little problem deflect you. 决不要因一点小问题就半途而废。

　　This special metal shield will deflect a bullet from its course. 这种特殊的金属盾将使子弹改变方向。

　　Devastate 毁坏，毁灭

　　原文：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。对于周期性出现大规模物种灭绝的可能性，引发了这样的假设：一颗具有长周期轨道的伴星体使其他天体从正常轨道偏离，导致其中一些天体变成流星掉落到地球，撞击时造成大范围破坏。

　　强化记忆：They intended to devastate the town at one stroke. 他们企图一举摧毁全城。

　　A fire or blood devastate and precious paper-historical documents completely. 一场大火或者一场洪水足以使珍贵的纸质资料全部摧毁。

　　Collision 冲突，碰撞

　　原文：The force of collision spewed large amounts of debris into the atmosphere, darkening the skies for several years before the finer particles settled. 碰撞的力量把大量碎片喷射到大气中，在这些细小颗粒沉积之前好几年的时间里天空都是灰蒙的。

　　强化记忆：There was a slight collision but my car was undamaged. 虽有轻微碰撞，但我的汽车没有损坏。

　　A collision with parliament could ruin the government's plans. 与议会冲突可能使政府的计划成为泡影。

　　Herbivore 食草动物

　　原文：This caused massive starvation first of herbivores and subsequently of carnivores. 这首先会造成草食动物大规模饿死，接着就是肉食动物大规模饿死。

　　强化记忆：Panda's are classified as carnivores but they mainly have a diet of an herbivore. 大熊猫被归为食肉动物，但它们饮食更像食草动物。

　　Carnivore 食肉动物

　　原文：This caused massive starvation first of herbivores and subsequently of carnivores. 这首先会造成草食动物大规模饿死，接着就是肉食动物大规模饿死。

　　强化记忆：I did mostly vegetarian food but put a couple of meat dishes out for the carnivores. 我基本上吃素，但是我会给吃肉的人准备一些肉食。

　　It is a carnivore, but it doesn't have any teeth. 它是一种食肉动物，却没有牙齿。

　　Iridium 铱(化学元素)

　　原文：One interesting test of the Alvarez hypothesis is based on the presence of the rare-earth element iridium (Ir). Alvarez 假说基于稀土元素铱的出现做了一个非常有趣的实验。

　　强化记忆：Here are some pens with gold or iridium nibs. 这里是金笔和铱金笔

　　Indeed, two iridium layers have been found in some places. 确实，有些地方发现了有两个铱层。

　　Presumably 大概，可能

　　原文：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。因小行星碰撞而被抛进到大气中的碎片可能会含有大量铱元素，并且大气流会把这些物质带到全球各地。

　　强化记忆： Presumably this is where the accident happened. 这大概就是事故现场。

　　Presumably she had been changed on to a later shift. 想必她改值了夜班。

　　Sedimentary 沉淀的

　　原文：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. 白垩纪时期与第三纪时期交替之间的沉积物的研究显示：在这两个时期的交替时期，铱元素的含量急剧增加。

　　强化记忆： It is useful in discussing the nature of sedimentary deposits. 它在讨论沉积物的性质时是有用的。

　　Loose sediments may be changed into solid sedimentary rocks. 松散的沉积物可以变成坚硬的沉积岩。

　　Crater 弹坑，火山口

　　原文：An asteroid of this size would be expected to leave an immense crater, even if the asteroid itself was disintegrated by the impact. 按理说，这样大小的一个行星，即使受到冲击碎裂之后也会留下一个巨大的陨石坑。

　　强化记忆：The blast blew a gaping crater in the road. 爆炸把道路撕开了一个大坑。

　　They came to the lip of a dead crater. 他们来到了一个死火山口。

　　Quartz 石英

　　原文：The intense heat of the impact would produce heat-shocked quartz in many types of rock. 撞击所释放的极度高温使得许多种岩石产生热冲击石英。

　　强化记忆：The quartz watch keeps good time. 石英表走时准。

　　There is a great deal quartz in those mountains. 那些山里蕴藏着大量石英。