The Evolutionary Mystery: Crocodile Survives
A Even though crocodiles have existed for 200 million years, they’re anything but primi-tive. As crocodiles’ ancestors, crocodilia came to adapt to an aquatic lifestyle. When most of the other contemporary reptiles went extinct, crocodiles were able to make it because their bodies changed and they adapted better to the climate. They witnessed the rise and fall of the dinosaurs, which once ruled the planet, and even the 65 million years of alleged mammalian dominance didn’t wipe them off. Nowadays, the crocodiles and alligators are not that different from their prehistoric ancestors, which proves that they were (and still are) incredibly adaptive.
B The first crocodile-like ancestors came into existence approximately 230 million years ago, and they had many of the features which make crocodiles natural and perfect stealth hunters: streamlined body, long tail, protective armour and long jaws. They are born with four short, webbed legs, but this does not mean that their capacity to move on the ground shall ever be underestimated. When they move, they are so fast that you won’t even have any chance to try making the same mistake again by getting too close, especially when they’re hunting.
C Like other reptiles, crocodiles are poikilothermal animals (commonly known as cold-blooded, whose body temperature changes with that of the surroundings) and conse-quently, require exposure to sunlight regularly to raise body temperature. When it is too hot, they would rather stay in water or shade. Compared with mammals and birds, crocodiles have a slower metabolism, which makes them less vulnerable to food short-age. In the most extreme case, a crocodile can slow its metabolism down even further, to the point that it would survive without food for a whole year, enabling them to outlive mammals in relatively volatile environments.
D Crocodiles have a highly efficient way to prey catching. The prey rarely realises there might be a crocodile under the water because the crocodile makes a move without any noise or great vibration when spotting its prey. It only keeps its eyes above the water level. As soon as it feels close enough to the victim, it jerks out of the water with its wide open jaws. Crocodiles are successful because they are capable of switching feeding methods. It chases after fish and snatches birds at the water surface, hides in the waterside bushes in anticipation of a gazelle, and when the chance to ambush presents itself, the crocodile dashes forward, knocks the animal out with its powerful tail and then drags the prey into the water to drown.
E In many crocodilian habitats, the hot season brings drought that dries up their hunting grounds, leaving it harder for them to regulate body temperatures. This actually allowed reptiles to rule. For instance, many crocodiles can protect themselves by digging holes and covering themselves in mud, waiting for months without consuming any food or water until the rains finally return. They transform into a quiescent state called aestiva-tion.
F The majority of crocodilian is considered to go into aestivation during the dry season. In a six-year study by Kennett and Christian, the King Crocodiles, a species of Australian freshwater crocodiles, spent nearly four months a year underground without access to water resources. Doubly labelled water was applied to detect field metabolic rates and water flux, and during some years, plasma fluid samples were taken once a month to keep track of the effects of aestivation regarding the accumulation of nitrogenous wastes and electrolyte concentrations.
G The study discovered that the crocodiles’ metabolic engines function slowly, creating waste and exhausting water and fat reserves. Waste is stored in the urine, becoming more and more concentrated. Nevertheless, the concentration of waste products in blood doesn’t fluctuate much, allowing the crocodiles to carry on their normal functions. Besides, even though the crocodiles lost water reserves and body weight when under-ground, the losses were proportional; upon emerging, the aestivating animals had no dehydration and displayed no other harmful effects such as a slowed-down growth rate. The two researchers reckon that this capacity of crocodiles to get themselves through the harsh times and the long starvation periods is sure to be the answer to the crocodil-ian line’s survival throughout history.
Questions 15 – 21
Reading Passage 2 has seven paragraphs, A-G.
Choose the correct heading for each paragraph from the list of headings below.
Write the correct number, i-xi, in boxes 15-21 on your answer sheet.
List of Headings
i The favourable feature in the impact of a drought
ii A unique finding that was recently achieved
iii Slow metabolism which makes crocodile a unique reptile
iv The perfectly designed body for a great land roamer
v Shifting eating habits and food intake
vi A project on a special mechanism
vii Regulating body temperature by the surrounding environment
viii Underwater aid in body structure offered to a successful predator
ix A historical story for the supreme survivors
x What makes the crocodile the fastest running animal on land
xi The competition between the crocodiles and other animals
- 15.Paragraph A
- 16.Paragraph B
- 17.Paragraph C
- 18.Paragraph D
- 19.Paragraph E
- 20.Paragraph F
- 21.Paragraph G
Questions 22 – 27
Complete the summary below.
Choose NO MORE THAN TWO WORDS from the passage for each answer.
Write your answers in boxes 22-27 on your answer sheet.
![图片[1]-9分达人阅读第27套P2-The Evolutionary Mystery: Crocodile Survives-kingreturn](http://tvax1.sinaimg.cn/large/008vvLZuly1h7bvpuop6dj30eo06qadc.jpg)
![图片[2]-9分达人阅读第27套P2-The Evolutionary Mystery: Crocodile Survives-kingreturn](http://tvax1.sinaimg.cn/large/008vvLZuly1h7bvq74o4mj30eo04jwgo.jpg)
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PASSAGE 2Questions 15 – 27
Questions 15 – 21
Reading Passage 2 has seven paragraphs, A-G.
Choose the correct heading for each paragraph from the list of headings below.
Write the correct number, i-xi, in boxes 15-21 on your answer sheet.
- i The favourable feature in the impact of a drought
- ii A unique finding that was recently achieved
- iii Slow metabolism which makes crocodile a unique reptile
- iv The perfectly designed body for a great land roamer
- v Shifting eating habits and food intake
- vi A project on a special mechanism
- vii Regulating body temperature by the surrounding environment
- viii Underwater aid in body structure offered to a successful predator
- ix A historical story for the supreme survivors
- x What makes the crocodile the fastest running animal on land
- xi The competition between the crocodiles and other animals
- 15. Paragraph Aix
- 16. Paragraph Biv
- 17. Paragraph Ciii
- 18. Paragraph Dv
- 19. Paragraph Ei
- 20. Paragraph Fvi
- 21. Paragraph Gii
Questions 22 – 27
Complete the summary below.
Choose NO MORE THAN TWO WORDS from the passage for each answer.
Write your answers in boxes 22-27 on your answer sheet.
Aestivation
In many places inhabited by crocodilians, most types of crocodiles have evolved a successful scheme to survive in the drought brought by a22hot season/dry season. According to Kennett and Christian’s six-year study of Australian freshwa-ter crocodiles’ aestivation, they found aestivating crocodiles spent around23four monthsof the year and had no access to24water resources. The amount of water in the body declined proportionately with25body weight; thus there is no sign of26dehydrationand other health-damaging impact on the crocodiles even after an aestivation period. This super capacity helps crocodiles endure the tough drought without slowing their speed of27growth.
进化奇迹 ：鳄鱼的存活
A 尽管鳄鱼已经存在了两亿年之久，但 它们一点儿都不“原始”。作为鳄鱼的 祖先，鳄目开始适应水生的生活方式。当多数同时代的爬行动物灭绝时，鳄 鱼能够幸免于难是因为它们的身体发 生了改变，更好地适应了环境的变化。恐龙一度是地球的主宰者，而鳄鱼则 见证了它们的存亡 ；甚至在经历了所 谓的哺乳类动物占主导的 6500 万年后，鳄鱼仍然存活了下来。现在的鳄 鱼和短吻鳄与它们的史前祖先没有太大的不同，这也证明了它们的适应能 力从过去到现在一直很强。
B 鳄鱼最早的祖先大约出现在两亿三千 年前，其具有的许多特点使之成为天 然的隐形猎手 ：流线身型、长长的尾 巴、坚硬的鳞甲以及长吻。它们天生 四肢短小，趾间有蹼，但这并不影响 它们在地面快速爬行。当鳄鱼行动时，速度之快以至于你都没有第二次机会 去犯下离它太近的错误，特别是在它 们捕猎时。
C 鳄鱼和其他爬行动物一样，属于变温动物（一般称为冷血动物，体温会随 环境温度的变化而变化）。因此，它们 需要时常晒太阳以提升体温。不过太 热的时候，它们更愿意待在水里或阴 凉处。与哺乳动物和鸟类相比，鳄鱼 的新陈代谢更慢一些，这使它们能够 更好地应对食物短缺。在最为极端的 条件下，鳄鱼会进一步减缓新陈代谢 的速度，达到一年可以不进食的程度，
这也使得它在相对不稳定的环境中比 哺乳动物活得更久。
D 鳄鱼捕食的效率极高。猎物几乎意识 不到水下有鳄鱼的存在，因为当鳄鱼 发现猎物时，不会发出很大的声响或 制造太大的水波。它只是将眼睛露出 水面。一旦判定距离足够近，它们就 会张大嘴窜出水面。鳄鱼成功的概率 很高，因为它们会变换进食方式。它 们会在水面追击鱼类或捕食鸟类，也 会潜伏在水边的灌木丛中等待瞪羚，一旦时机到来，鳄鱼便会向前猛冲， 用强有力的尾巴击倒猎物，然后将其 拖入水中直至猎物溺亡。
E 在许多鳄鱼的栖息地，酷热的季节会 引发干旱，进而导致捕食的区域变得 十分干燥，因此，鳄鱼就会很难调控 自己的体温。实际上，正是这点使得 爬行动物得以称雄。例如，许多鳄鱼都会通过挖洞藏在泥中来保护自己， 不进食不饮水等待数月，直到降雨再 次来临。这种静止的状态叫作夏眠。
F 人们认为大部分鳄鱼会在干旱的季节 进入夏眠。肯内特（Kennett）和克里 斯 琴（Christian） 进 行 了 一 项 为 期 6 年的研究，研究对象是澳大利亚的一 种淡水鳄鱼，叫作鳄鱼王（the King Crocodiles），这种鳄鱼每年有 4 个月的时间潜伏在地下，不接触水源。研 究运用双重标记的水来检测它们新陈 代谢的速率以及水通量。有几年他们 还会每月检测一次等离子的流体样本，基于含氮废物的累积和电解质的浓度 来跟踪记录鳄鱼夏眠的状态。
G 研究发现，鳄鱼新陈代谢的机能缓慢， 这会产生排泄物并消耗水和脂肪储备。 排泄物会储存在尿液中，使其浓度越 来越高。不过血液中排泄物的浓度变 化不大，所以鳄鱼才可以维持正常生 活。此外，虽然鳄鱼在地下会消耗水 分和减少体重，但这种损耗是均衡的 ； 夏眠的动物在复出时既不会脱水，也 不会出现像减缓生长等有害影响。鳄 鱼能够经受极端的时期和漫长的饥饿 而存活下来，两位研究员认为，这种 能力很好地解释了为什么鳄鱼一族能 够经历漫长历史，存活至今。
- 第 15 / 40 题正确答案： ix
我的答案： No answer
解析
A 段开头便提到鳄鱼存在了两亿多年，但它们并不原始。根据上下文判断，原因有二。第一，还有比鳄鱼更原始的动物，比如恐龙。相比恐龙，它谈不上原始。第二，鳄 鱼能够通过自身的调整来适应环境的剧变，这一点特征很高级。同时代的动物早就 灭亡了，唯独鳄鱼存活至今，而且与最初的鳄鱼祖先差别不大，足以说明其强大的 适应能力。纵观所有的选项，只有 ix A historical story for the supreme survivors 中有谈 到历史相关，而 supreme survivors 这种卓越的幸存者自然指的是鳄鱼。因此，本题的 答案为 ix。
- 第 16 / 40 题正确答案： iv
我的答案： No answer
解析
B 段的第 1 句话就是本段的核心主旨句，主要陈述了鳄鱼的 features，很多生理特征 让它成为完美的猎手，包括 streamlined body, long tail, protective armour and long jaws。在所有的选项中，能概括本段的只有 iv The perfectly designed body for a great land roamer。其中 perfectly designed body 就是指本段提到的 features。注意，本题不能选 x What makes the crocodile the fastest running animal on land，因为段中没有说鳄鱼是 在陆地上移动最快的生物。因此，本题的答案为 iv。
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- 第 17 / 40 题正确答案： iii
我的答案： No answer
解析
C 段开头第 1 句话介绍了鳄鱼是 poikilothermal animals（变温动物），这种动物共有的特点便是体温会随外界环境的变化而变化。接下来提到鳄鱼相比哺乳动物和鸟类， 新陈代谢速度更慢，在恶劣条件下会进一步减缓新陈代谢的速度，达到一年可以不 进食的程度，这也使得它比哺乳动物活得更久。这也说明，新陈代谢慢正是鳄鱼区 别于其他动物的地方。选项 vii，即环境调节体温这是变温动物的基本特征，不足以 概括整段大意。选项 iii Slow metabolism which makes crocodile a unique reptile（新陈 代谢慢让鳄鱼们很独特）正好呼应了本段的核心观点。因此，本题的答案为 iii。
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- 第 18 / 40 题正确答案： v
我的答案： No answer
解析
D 段的第 1 句话是本段的核心主旨句，提出鳄鱼有非常高效的捕猎方式。接下来就是之所以高效的原因。首先说了鳄鱼经常突然袭击猎物，因此成功率颇高。在中后段， 又说鳄鱼很成功是因为它们能够改变进食方式或捕食策略，会在水面追击鱼类或捕 食鸟类，也会潜伏在水边的灌木丛中等待瞪羚。其中 switching feeding methods 替换 选项 shifting eating habits。因此，本题的答案为 v。
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- 第 19 / 40 题正确答案： i
我的答案： No answer
解析
E 段第 1 句话说太过炎热会导致干旱，但是鳄鱼有种方法保护自己，比如 aestivation （夏眠）。在选项中，i The favourable feature in the impact of a drought（鳄鱼抵抗干旱的有 利特征），这里的有利特征就是指“夏眠”。因此，本题的答案为 i。
正确答案： vi
我的答案： No answer
解析
F 段中，讲述了一个由 Kennett 和 Christian 所领导的进行了 6 年的研究，主要是追踪 鳄鱼夏眠时的生理特点。选项 vi A project on a special mechanism 中，mechanism 意为“机制，行为方式”，指的就是鳄鱼的“夏眠”行为。因此，本题的答案为 vi。
- 第 21 / 40 题正确答案： ii
我的答案： No answer
解析
G 段紧接着 F 段的研究内容，开始描述研究结果。研究发现鳄鱼在夏眠的时候消耗 少，而且损失的营养对其本身没有负面影响。在选项中，ii A unique finding that was recently achieved 最为合适。因此，本题的答案为 ii。
- 22 / 40 题正确答案： hot season/dry season
我的答案： No answer
解析
题干 ：在鳄鱼栖息的许多地方，大多数种类的鳄鱼进化出一种成功的机制，可以在什么引起的干旱下存活下来。空白处需要填写的是单数名词或名词短语。通过做之 前的题目，我们已经知道这种成功的机制说的就是 aestivation，通过关键词 drought 可定位至 E 段第 1 句，in many crocodilian habitats 对应题干 in many places inhabited by crocodilians，从而确定干旱是由 hot season 引起的。另外，在 aestivation 第二次出 现时，F 段开头再次强调了鳄鱼会在 dry season 进入夏眠。因此，本题的答案为 hot season/dry season。
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- 第 23 / 40 题正确答案： four months
我的答案： No answer
解析
题干 ：……他们发现夏眠的鳄鱼会在一年中花费大约多长时间不接触什么。第 23 和 24 题在一句话之中，所以定位回到原文也一定距离很近。本题通过人名 Kennett and Christian 定位到 F 段第 2 句，这一句提到了一年中近 4 个月不接触水源。其中 nearly 同义替换题干 around，year 原词重现，without access to 同义替换题干 had no access to。因此，23 题的答案为 four months
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- 第 24 / 40 题正确答案： water resources
我的答案： No answer
解析
题干 ：……他们发现夏眠的鳄鱼会在一年中花费大约多长时间不接触什么。第 23 和 24 题在一句话之中，所以定位回到原文也一定距离很近。本题通过人名 Kennett and Christian 定位到 F 段第 2 句，这一句提到了一年中近 4 个月不接触水源。其中 nearly 同义替换题干 around，year 原词重现，without access to 同义替换题干 had no access to。因此，23 题的答案为 four months，24 题的答案为 water resources。
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- 第 25 / 40 题正确答案： body weight
我的答案： No answer
解析
题干 ：体内的水含量与什么成比例减少。原文 G 段开头提及了鳄鱼会消耗自身的水 分（water reserves）和脂肪，继续往后扫读，第 4 句再次提到水分，proportional 替 换了题干 proportionately，与水分一词并列的名词成分应为答案。因此，本题的答案 为 body weight。
- 第 26 / 40 题正确答案： dehydration
我的答案： No answer
解析
题干 ：因此，甚至在夏眠时期，没有什么和其他损害鳄鱼健康的迹象出现。空白处 是与 other health-damaging impact 并列的一种迹象。文中 other harmful effects 替换了 题干 other health-damaging impact，往前寻找与其并列的成分。因此，本题的答案为 dehydration。
