雅思阅读每日习题系列：Great Migrations

　　本文整理了雅思阅读每日习题系列：Great Migrations供大家参考使用，预祝各位考生在雅思阅读考试中取得优异的成绩！

　　Great Migrations

　　Animal migration, however it is defined, is far more than just the movement of animals. It can loosely be described as travel that takes place at regular intervals ?— often in an annual cycle — that may involve many members of a species, and is rewarded only after a long journey. It suggests inherited instinct. The biologist Hugh Dingle has identified five characteristics that apply, in varying degrees and combinations, to all migrations. They are prolonged movements that carry animals outside familiar habitats; they tend to be linear, not zigzaggy; they involve special behaviours concerning preparation (such as overfeeding) and arrival; they demand special allocations of energy. And one more: migrating animals maintain an intense attentiveness to the greater mission, which keeps them undistracted by temptations and undeterred by challenges that would turn other animals aside.

　　An arctic tern, on its 20,000 km flight from the extreme south of South America to the Arctic circle, will take no notice of a nice smelly herring offered from a bird-watcher's boat along the way. While local gulls will dive voraciously for such handouts, the tern flies on. Why? The arctic tern resists distraction because it is driven at that moment by an instinctive sense of something we humans find admirable: larger purpose. In other words, it is determined to reach its destination. The bird senses that it can eat, rest and mate later. Right now it is totally focused on the journey; its undivided intent is arrival.

　　Reaching some gravelly coastline in the Arctic, upon which other arctic terns have converged, will serve its larger purpose as shaped by evolution: finding a place, a time, and a set of circumstances in which it can successfully hatch and rear offspring.

　　But migration is a complex issue, and biologists define it differently, depending in part on what sorts of animals they study. Joe! Berger, of the University of Montana, who works on the American pronghorn and other large terrestrial mammals, prefers what he calls a simple, practical definition suited to his beasts: 'movements from a seasonal home area away to another home area and back again'. Generally the reason for such seasonal back-and-forth movement is to seek resources that aren't available within a single area year-round.

　　But daily vertical movements by zooplankton in the ocean — upward by night to seek food, downward by day to escape predators — can also be considered migration. So can the movement of aphids when, having depleted the young leaves on one food plant, their offspring then fly onward to a different host plant, with no one aphid ever returning to where it started.

　　Dingle is an evolutionary biologist who studies insects. His definition is more intricate than Berger's, citing those five features that distinguish migration from other forms of movement. They allow for the fact that, for example, aphids will become sensitive to blue light (from the sky) when it's time for takeoff on their big journey, and sensitive to yellow light (reflected from tender young leaves) when it's appropriate to land. Birds will fatten themselves with heavy feeding in advance of a long migrational flight. The value of his definition, Dingle argues, is that it focuses attention on what the phenomenon of wildebeest migration shares with the phenomenon of the aphids, and therefore helps guide researchers towards understanding how evolution has produced them all.

　　Human behaviour, however, is having a detrimental impact on animal migration. The pronghorn, which resembles an antelope, though they are unrelated, is the fastest land mammal of the New World. One population, which spends the summer in the mountainous Grand Teton National Park of the western USA, follows a narrow route from its summer range in the mountains, across a river, and down onto the plains. Here they wait out the frozen months, feeding mainly on sagebrush blown clear of snow. These pronghorn are notable for the invariance of their migration route and the severity of its constriction at three bottlenecks. If they can't pass through each of the three during their spring migration, they can't reach their bounty of summer grazing; if they can't pass through again in autumn, escaping south onto those windblown plains, they are likely to die trying to overwinter in the deep snow. Pronghorn, dependent on distance vision and speed to keep safe from predators, traverse high, open shoulders of land, where they can see and run. At one of the bottlenecks, forested hills rise to form a V, leaving a corridor of open ground only about 150 metres wide, filled with private homes. Increasing development is leading toward a crisis for the pronghorn, threatening to choke off their passageway.

　　Conservation scientists, along with some biologists and land managers within the USA's National Park Service and other agencies, are now working to preserve migrational behaviours, not just species and habitats. A National Forest has recognised the path of the pronghorn, much of which passes across its land, as a protected migration corridor. But neither the Forest Service nor the Park Service can control what happens on private land at a bottleneck. And with certain other migrating species, the challenge is complicated further — by vastly greater distances traversed, more jurisdictions, more borders, more dangers along the way. We will require wisdom and resoluteness to ensure that migrating species can continue their journeying a while longer.

　　Questions 14-18

　　Do the following statements agree with the information given in Reading Passage 2?

　　In boxes 14-18 on your answer sheet, write

　　TRUE if the statement agrees with the information

　　FALSE if the statement contradicts the information

　　NOT GIVEN if there is no information on this

　　14 Local gulls and migrating arctic terns behave in the same way when offered food.

　　15 Experts' definitions of migration tend to vary according to their area of study.

　　16 Very few experts agree that the movement of aphids can be considered migration.

　　17 Aphids' journeys are affected by changes in the light that they perceive.

　　18 Dingle's aim is to distinguish between the migratory behaviours of different species.

　　Questions 19-22

　　Complete each sentence with the correct ending, A-G, below.

　　Write the correct letter, A-G, in boxes 19-22 on your answer sheet.

　　19 According to Dingle, migratory routes are likely to

　　20 To prepare for migration, animals are likely to

　　21 During migration, animals are unlikely to

　　22 Arctic terns illustrate migrating animals' ability to

　　A be discouraged by difficulties.

　　B travel on open land where they can look out for predators.

　　C eat more than they need for immediate purposes.

　　D be repeated daily.

　　E ignore distractions.

　　F be governed by the availability of water.

　　G follow a straight line.

　　Questions 23-26

　　Complete the summary below.

　　Choose ONE WORD ONLY from the passage for each answer.

　　Write your answers in boxes 23-26 on your answer sheet.

　　The migration of pronghorns

　　Pronghorns rely on their eyesight and 23 __________ to avoid predators. One particular population's summer habitat is a national park, and their winter home is on the 24 __________, where they go to avoid the danger presented by the snow at that time of year. However, their route between these two areas contains three 25 __________. One problem is the construction of new homes in a narrow 26 __________ of land on the pronghorns' route.

　　下页是该篇阅读题目的答案解析，一起来具体的了解一下吧：

　　Question 14

　　答案: False

　　关键词: local gulls, arctic terns, food

　　定位原文: 第2段前两句“An arctic tern, on its 20,000 km flight…”

　　解题思路: local gulls 会为了herring 这样的 handouts 而 voraciously 俯冲下来，然而arctic tern却会继续飞行，显然二者在面对食物时表现得并不一样。不考虑有可能很不多不认识的单词，但看while这个提示词又明确强化了是不一样的，与题干信息相悖。

　　Question 15

　　答案: True

　　关键词: expert's definitions, vary, area of study

　　定位原文: 第3段第1句“But migration is a complex…”迁徙是个复杂的问题，生物学家依据研究的动物不同对定义也各不相同。

　　解题思路: 只需按照“专家的定义”找到原文中的相应描述即可，答案与题目“专家们对于迁徙的定义往往会根据他们的研究领域而各有不同”为同义表达。

　　Question 16

　　答案： Not Given

　　关键词： very few experts agree, movement of aphids

　　定位原文：第4段前两句“But daily vertical movements by…”

　　解题思路: 本题具有一定的迷惑性。“蚜虫移动”这个信息不难定位，原文也以事实陈述的口吻指出：浮游生物和蚜虫的移动确实可以被视为某种形式的迁徙。但此题是一道典型的“将事实与观点相混淆”思路的判断题，题干说“基本没有什么专家认同这个看法”，是明确的“专家观点表达”，与原文的“事实陈述”既不能说是矛盾，也不能说是一致，而是Not Given。

　　Question 17

　　答案： True

　　关键词： aphids' journeys, affected, changes in the light

　　定位原文： 第5段第3句“..., aphids will become sensitive to blue light (from the sky) when it's time for takeoff on their big journey…” 对蓝光和黄光敏感…….

　　解题思路：可能未必认识aphids (蚜虫)这个单词，但它在文中作为昆虫名并没有被替换。阅读定位句可知，这种生物确实会在不同的情況下分别对蓝光和黄光更加敏感，也就是“会受到光色变化的影响”，答案为True。

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　　Question 18

　　答案: False

　　关键词： Dingle's aim, distinguish

　　定位原文： 第5段最后一句“The value of his definition, Dingle…”

　　解题思路: 由于有Dingle这个大写人名，本题定位不难。Dingle的目的在于找到迁徙行为的共性，与题干所表述的“目标在于区分不同物种迁徙行为之间的差异”是两个不同的意思。

　　Question 19

　　答案: G

　　关键词： Dingle, migratory routes, likely

　　定位原文： 第1段的第4、5句“The biologist Hugh Dingle has identified five…”

　　解题思路： 题干说“按照Dingle的说法，迁徙的路线往住会______” 回到原文中Dingle这个人名不难找到，route (路线)这个意思却是通过linear和 zigzaggy这两个用以描述“路线”是平直还是曲折的形容词来间接表达的，需要考生认识其中至少一个才能更准确定位。而一旦定位之后确定答案则很容易，为G项：follow a straight line (沿着一条直线)。

　　Question 20

　　答案： C

　　关键词： prepare for, likely to

　　定位原文：第1段第5句“…; they involve special behaviours concerning preparation…”

　　解题思路：题干说“为了给迁徙做准各，动物们往往会_____”。prepare这个题干中的定位信息在原文中仅仅改了词性，变成了名词preparation，很容易被找到;而括号里对于“做准备”的举例说明overfeeding也不是困难的词汇，可以轻松得出答案为C: eat more than they need for immediate purposes (吃得比它们当下立刻就需要的要多)。

　　Question 21

　　答案： A

　　关键词： during migration, unlikely to

　　定位原文：第1段最后一句“And one more: migrating…”

　　解题思路：题干说“在迁徙过程中，动物们一般不会______”，此题比较有迷惑性，原因在于原文中给出了两个否定性信息：undistracted by temptations 和 undeterred by challenges that would turn other animals aside，分别对应于选项E和选项A。注意：选项E和A所描述内容的方向是相反的。根据题干中的unlikely，可得出答案为A: be discouraged by difficulties，即“不会被困难阻挡”，如果选E的话，则与文意相反。

　　Question 22

　　答案： E

　　关键词： Arctic terns, illustrate, ability

　　定位原文： 第2段前四句 “An arctic tern, on its 20,000 km flight from …”

　　解题思路: 题干说“北极燕鸥证明了迁徙中的动物的______能力”。Arctic ton不难定位，但考生需要具备耐心，在第一次找到定位词的句子里没有提供相关解题信息的时候继续向下阅读原文，直到看至第四句时能得出完整信息，答案为E: ignore distractions (忽视那些分散注意力的因素)。

　　Question 23

　　答案： speed

　　关键词： pronghorns, rely on, eyesight, predators

　　定位原文：第6段倒数第3句“Pronghorn, dependent on distance vision…”

　　解题思路： pronghorn这个词在文中出现在了两个部位。第一次是在第三段中，只是在介绍Joel Berger 的研究领域时被简短地一带而过，没有展开;第二次则是在文章的后两段中密集出现，此时才是真正说到了其迁徙行为的细节内容，是此部分summary题型对应的正文部分。题干说“叉角羚依赖它们的视力和_____来躲避捕食者”。対比原文中与vision形成并列关系的内容，可得答案为speed。

　　Question 24

　　答案: plains

　　关键词: summer habitat, national park, winter home

　　定位原文: 第6段第3、4句“One population, which spends the summer in the mountainous…”

　　解题思路：题干说“某个特定种群(叉角羚)的夏季栖息地是一个国家公园，而它们的冬季家园则位于_____”。“夏季”和“国家公园”这两个信息都不难在文中找到，但包含这两个信息的句子里提供的地点“平原”却不容易被确定为答案，原因在于本句中并没有明确提及“冬季”这个信息。考生需要耐心向下再阅读一句，找到“冬季”的同义替换frozen months，从而用here这个地点指代词来确认，答案为plains。

　　Question 25

　　答案： bottlenecks

　　关键词： route, three

　　定位原文：第6段第5句“These pronghorn are notable for…”

　　解题思路：题干说“它们在这两个区域之间的迁徙路线包含三个_____”。其实只需找到文中明确提及“三”这个数目的所指对象即可，答案为bottlenecks。

　　Question 26

　　答案： corridor

　　关键词：problem, construction of new homes, narrow

　　定位原文：第6段倒数第2句“At one of the bottlenecks, forested hills…”

　　解题思路：题干说“问题之一来自叉角羚迁徙路线上一条狭长_____上的新建房屋”。本题的难度来自于使用了narrow来同义替换“只有150米宽”这一具体的细节信息，可能会给定位造成一定障碍。而一旦成功定位即可得出答条为corridor。

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