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剑桥雅思阅读11真题及答案解析(test3)
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剑桥雅思阅读11原文(test3)
READING PASSAGE 1
You should spend about 20 minutes on Questions 1-13,
which are based on Reading Passage 1 below.
THE STORY OF SILK
The history of the world’s most luxurious fabric, from
ancient China to the present day
Silk is a fine, smooth material produced from the cocoons —
soft protective shells — that are made by mulberry silkworms
(insect larvae). Legend has it that it was Lei Tzu, wife of the Yellow
Emperor, ruler of China in about 3000 BC, who discovered
silkworms. One account of the story goes that as she was taking
a walk in her husband’s gardens, she discovered that silkworms
were responsible for the destruction of several mulberry trees.
She collected a number of cocoons and sat down to have a rest.
It just so happened that while she was sipping some tea, one of
the cocoons that she had collected landed in the hot tea and
started to unravel into a fine thread. Lei Tzu found that she could
wind this thread around her fingers. Subsequently, she
persuaded her husband to allow her to rear silkworms on a grove
of mulberry trees. She also devised a special reel to draw the
fibres from the cocoon into a single thread so that they would be
strong enough to be woven into fabric. While it is unknown just
how much of this is true, it is certainly known that silk cultivation
has existed in China for several millennia.
Originally, silkworm farming was solely restricted to women,
and it was they who were responsible for the growing, harvesting
and weaving. Silk quickly grew into a symbol of status, and
originally, only royalty were entitled to have clothes made of silk.
The rules were gradually relaxed over the years until finally during
the Qing Dynasty (1644-1911 AD), even peasants, the lowest
caste, were also entitled to wear silk. Sometime during the Han
Dynasty (206 BC-220 AD), silk was so prized that it was also used
as a unit of currency. Government officials were paid their salary
in silk, and farmers paid their taxes in grain and silk. Silk was also
used as diplomatic gifts by the emperor. Fishing lines, bowstrings,
musical instruments and paper were all made using silk. The
earliest indication of silk paper being used was discovered in the
tomb of a noble who is estimated to have died around 168 AD.
Demand for this exotic fabric eventually created the lucrative
trade route now known as the Silk Road, taking silk westward and
bringing gold, silver and wool to the East. It was named the Silk
Road after its most precious commodity, which was considered
to be worth more than gold. The Silk Road stretched over 6,000
kilometres from Eastern China to the Mediterranean Sea,
following the Great Wall of China, climbing the Pamir mountain
range, crossing modern-day Afghanistan and going on to the
Middle East, with a major trading market in Damascus. From
there, the merchandise was shipped across the Mediterranean
Sea. Few merchants travelled the entire route; goods were
handled mostly by a series of middlemen.
With the mulberry silkworm being native to China, the
country was the world’s sole producer of silk for many hundreds
of years. The secret of silk-making eventually reached the rest of
the world via the Byzantine Empire, which ruled over the
Mediterranean region of southern Europe, North Africa and the
Middle East during the period 330-1453 AD. According to
another legend, monks working for the Byzantine emperor
Justinian smuggled silkworm eggs to Constantinople (Istanbul in
modern-day Turkey) in 550 AD, concealed inside hollow bamboo
walking canes. The Byzantines were as secretive as the Chinese,
however, and for many centuries the weaving and trading of silk
fabric was a strict imperial monopoly. Then in the seventh century,
the Arabs conquered Persia, capturing their magnificent silks in
the process. Silk production thus spread through Africa, Sicily and
Spain as the Arabs swept through these lands. Andalusia in
southern Spain was Europe’s main silk-producing centre in the
tenth century. By the thirteenth century, however, Italy had
become Europe’s leader in silk production and export. Venetian
merchants traded extensively in silk and encouraged silk growers
to settle in Italy. Even now, silk processed in the province of Como
in northern Italy enjoys an esteemed reputation.
The nineteenth century and industrialisation saw the
downfall of the European silk industry. Cheaper Japanese silk,
trade in which was greatly facilitated by the opening of the Suez
Canal, was one of the many factors driving the trend. Then in the
twentieth century, new manmade fibres, such as nylon, started to
be used in what had traditionally been silk products, such as
stockings and parachutes. The two world wars, which interrupted
the supply of raw material from Japan, also stifled the European
silk industry. After the Second World War, Japan’s silk
production was restored, with improved production and quality
of raw silk. Japan was to remain the world’s biggest producer of
raw silk, and practically the only major exporter of raw silk, until
the 1970s. However, in more recent decades, China has gradually
recaptured its position as the world’s biggest producer and
exporter of raw silk and silk yarn. Today, around 125,000 metric
tons of silk are produced in the world, and almost two thirds of
that production takes place in China.
Questions 1-9
Complete the notes below.
Choose ONE WORD ONLY from the passage for each answer.
Write your answers in boxes 1-9 on your answer sheet.
THE STORY OF SILK
Early silk production in China
Around 3000 BC, according to legend:
- silkworm cocoon fell into emperor’s wife’s 1 __________
- emperor’s wife invented a 2 __________ to pull out silk
fibres
Only 3 __________ were allowed to produce silk
Only 4 __________ were allowed to wear silk
Silk used as a form of 5 __________
- e.g. farmers’ taxes consisted partly of silk
Silk used for many purposes
- e.g. evidence found of 6 __________ made from silk around
168 AD
Silk reaches rest of world
Merchants use Silk Road to take silk westward and bring back
7 __________ and precious metals
550 AD: 8 __________ hide silkworm eggs in canes and take
them to Constantinople
Silk production spreads across Middle East and Europe
20th century: 9 __________ and other manmade fibres cause
decline in silk production
Questions 10-13
Do the following statements agree with the information in
Reading Passage 1?
In boxes 10-13 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
10 Gold was the most valuable material transported along
the Silk Road.
11 Most tradesmen only went along certain sections of the
Silk Road.
12 The Byzantines spread the practice of silk production
across the West.
13 Silk yarn makes up the majority of silk currently exported
from China.
READING PASSAGE 2
You should spend about 20 minutes on Questions 14-26,
which are based on Reading Passage 2 below.
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.
READING PASSAGE 3
You should spend about 20 minutes on Questions 27-40,
which are based on Reading Passage 3 below.
Preface to ‘How the other half thinks: Adventures in
mathematical reasoning’
A Occasionally, in some difficult musical compositions, there
are beautiful, but easy parts — parts so simple a beginner could
play them. So it is with mathematics as well. There are some
discoveries in advanced mathematics that do not depend on
specialized knowledge, not even on algebra, geometry, or
trigonometry. Instead they may involve, at most, a little
arithmetic, such as ‘the sum of two odd numbers is even’, and
common sense. Each of the eight chapters in this book illustrates
this phenomenon. Anyone can understand every step in the
reasoning.
The thinking in each chapter uses at most only elementary
arithmetic, and sometimes not even that. Thus all readers will
have the chance to participate in a mathematical experience, to
appreciate the beauty of mathematics, and to become familiar
with its logical, yet intuitive, style of thinking.
B One of my purposes in writing this book is to give readers
who haven’t had the opportunity to see and enjoy real
mathematics the chance to appreciate the mathematical way of
thinking. I want to reveal not only some of the fascinating
discoveries, but, more importantly, the reasoning behind them.
In that respect, this book differs from most books on
mathematics written for the general public. Some present the
lives of colorful mathematicians. Others describe important
applications of mathematics. Yet others go into mathematical
procedures, but assume that the reader is adept in using algebra.
C I hope this book will help bridge that notorious gap that
separates the two cultures: the humanities and the sciences, or
should I say the right brain (intuitive) and the left brain (analytical,
numerical). As the chapters will illustrate, mathematics is not
restricted to the analytical and numerical; intuition plays a
significant role. The alleged gap can be narrowed or completely
overcome by anyone, in part because each of us is far from using
the full capacity of either side of the brain. To illustrate our human
potential, I cite a structural engineer who is an artist, an electrical
engineer who is an opera singer, an opera singer who published
mathematical research, and a mathematician who publishes
short stories.
D Other scientists have written books to explain their fields
to non-scientists, but have necessarily had to omit the
mathematics, although it provides the foundation of their
theories. The reader must remain a tantalized spectator rather
than an involved participant, since the appropriate language for
describing the details in much of science is mathematics, whether
the subject is expanding universe, subatomic particles, or
chromosomes. Though the broad outline of a scientific theory
can be sketched intuitively, when a part of the physical universe
is finally understood, its description often looks like a page in a
mathematics text.
E Still, the non-mathematical reader can go far in
understanding mathematical reasoning. This book presents the
details that illustrate the mathematical style of thinking, which
involves sustained, step-by-step analysis, experiments, and
insights. You will turn these pages much more slowly than when
reading a novel or a newspaper. It may help to have a pencil and
paper ready to check claims and carry out experiments.
F As I wrote, I kept in mind two types of readers: those who
enjoyed mathematics until they were turned off by an unpleasant
episode, usually around fifth grade, and mathematics aficionados,
who will find much that is new throughout the book.
This book also serves readers who simply want to sharpen
their analytical skills. Many careers, such as law and medicine,
require extended, precise analysis. Each chapter offers practice in
following a sustained and closely argued line of thought. That
mathematics can develop this skill is shown by these two
testimonials:
G A physician wrote, ‘The discipline of analytical thought
processes [in mathematics] prepared me extremely well for
medical school. In medicine one is faced with a problem which
must be thoroughly analyzed before a solution can be found. The
process is similar to doing mathematics.’
A lawyer made the same point, ‘Although I had no
background in law — not even one political science course — I
did well at one of the best law schools. I attribute much of my
success there to having learned, through the study of
mathematics, and, in particular, theorems, how to analyze
complicated principles. Lawyers who have studied mathematics
can master the legal principles in a way that most others cannot.’
I hope you will share my delight in watching as simple, even
na?ve, questions lead to remarkable solutions and purely
theoretical discoveries find unanticipated applications.
Questions 27-34
Reading Passage 3 has seven sections, A-G.
Which section contains the following information?
Write the correct letter, A-G, in boxes 27-34 on your answer
sheet.
NB You may use any letter more than once.
27 a reference to books that assume a lack of mathematical
knowledge
28 the way in which this is not a typical book about
mathematics
29 personal examples of being helped by mathematics
30 examples of people who each had abilities that seemed
incompatible
31 mention of different focuses of books about mathematics
32 a contrast between reading this book and reading other
kinds of publication
33 a claim that the whole of the book is accessible to
everybody
34 a reference to different categories of intended readers of
this book
Questions 35-40
Complete the sentences below.
Choose ONE WORD ONLY from the passage for each answer.
Write your answers in boxes 35-40 on your answer sheet.
35 Some areas of both music and mathematics are suitable
for someone who is a __________.
36 It is sometimes possible to understand advanced
mathematics using no more than a limited knowledge of
__________.
37 The writer intends to show that mathematics requires
__________ thinking, as well as analytical skills.
38 Some books written by __________ have had to leave out
the mathematics that is central to their theories.
39 The writer advises non-mathematical readers to perform
__________ while reading the book.
40 A lawyer found that studying __________ helped even more
than other areas of mathematics in the study of law.
剑桥雅思阅读11原文参考译文(test3)
PASSAGE 1 参考译文：
丝绸的故事
世上最昂贵奢华织物的历史，从古代中国直到今天
丝绸是种细软、光滑的布料，产自桑蚕(该昆虫的幼体形态)制作出
的蚕茧——即其柔软的保护性外壳。传说中是嫘祖，即大约公元前三
千年时期的中国统治者黄帝的妻子，发现了蚕。其中一个故事是这样
描述的：当她漫步于自己丈夫的花园之中时，她发现几棵桑树之所以
生长遭受破坏正是由于树上的蚕虫。她收集了一些蚕茧并坐下来歇息。
正巧在她啜饮着一杯茶时，这些蚕茧中的一粒掉进了热茶中并开始松
散成为一根细丝。嫘祖发现她可以将这根丝线绕在自己的手指上。于
是，她说服了丈夫允许她在一片桑树林内养蚕。她还设计发明了一种
特殊的卷轴来将蚕茧中的纤维纺成丝线，这样它们就能足够强韧以编
纺成织物。虽然这个故事中究竟有多少真实成分我们不得而知，但有
一点是确定无疑的：丝绸的生产在中国早己存在了数千年之久。
起初，桑蚕业完全是只由女性来进行的，她们要负责种植、收获
和纺织。丝绸很快成为了一种社会地位的象征，最早只有皇室成员才
有资格穿着丝绸衣物。这些规矩在之后的年月里逐渐变得不那么严苛
了，直到最终在清朝(公元1644~1911年)时期，即使是最低阶层的农
民也有资格穿上丝绸了。在汉朝(公元前206~公元220年)的某个时期，
丝绸的身价昂贵到被用作某种形式的流通货币。朝廷官员的俸禄是用
丝绸来支付的，而农夫则用谷物和丝绸来完税。丝绸还被皇帝用作外
交礼物。渔线、弓弦、乐器和紙皆由丝绸制作而来。人类最早使用丝
质纸的证据发现于一位贵族的墓中，据估计此人大约死于公元168年。
人们对这种异域织物的大量需求最终催生出了现在被称为“丝绸
之路”的这样一条一本万利的贸易路线，向西输送丝绸而向东则运来
金、银和毛料。之所以叫做“丝绸之路”，正是以其最珍贵的商品而
得名，它被视为比黄金更贵重。“丝绸之路”从中国东部一路绵亘
6000多公里直达地中海，沿着中国长城的路线，攀越帕米尔山脊，穿
过今日的阿富汗并延伸到了中东地区，在大马士革有一个主要交易市
场。各种货物从那里再由船运跨过地中海销往各地。很少有商人会走
遍整条路线;货物大多是由一系列的中间经手人交接传递的。
由于桑蚕原产于中国，这个国家在许多个世纪里一直是全球唯一
的丝绸产地。丝绸制作的秘密最终是经由在公元330~1453年间统治
着地跨南欧、北非和中东的地中海地区的拜占庭帝国传到了世界上的
其他国家。根据另一个传说，为拜占庭皇帝查士丁尼(Justinian)服务
的僧侣们在公元550年将蚕卵藏在空心的竹子手杖里，偷偷带到了君
士坦丁堡(即今日土耳其的伊斯坦布尔)。然而，拜占庭人和中国人一样
守秘不宣，在很多个世纪里丝绸料子的纺织和贸易都受到帝国的严格
把控垄断。然后在七世纪，阿拉伯人征服了波斯，在此过程中掠获了
它们的华贵丝绸。丝绸生产由此随着阿拉伯人对非洲、西西里和西班
牙的扫荡而传遍了这些地方。西班牙南部的安达卢西亚在十世纪里是
欧洲的主要丝绸生产中心。不过到13世纪的时候，意大利则成为了欧
洲丝绸生产和出口的领军者。威尼斯商人们到处进行丝绸贸易并鼓励
制丝者来意大利定居。甚至是到了如今，意大利北部科莫省加工的丝
绸仍然享有盛誉。
19世纪和工业化目睹了欧洲丝绸产业的衰落。更为廉价的日本丝
绸，这种货物的贸易得到了苏伊士运河开通的极大推动，是促成这ー
衰落趋势的许多因素之一。接下来在20世纪里，新型人造纤维材料，
例如尼龙，开始应用在传统上一直使用丝绸的产品中，例如长筒袜和
降落伞。两次世界大战切断了来自日本的原材料供应，也扼杀了欧洲
丝绸产业。二战过后，日本的丝绸生产再度复工，生丝的制作工艺和
品质都有所提升。直到20世纪70年代之前，日本始终是世界上最大
的生丝生产者，实际上也是唯一的大规模生丝出口者。但是，在近几
十年里，中国逐渐重拾昔日地位，成为全球最大的生丝和丝线生产者
和出口国。今天，全世界大约生产125,000公吨的丝绸，其中几乎三
分之二的产量出自中国。
TEST 3 PASSAGE 2 参考译文：
大迁徙
动物迁徒，无论如何下定义，都远不只是动物群的移动而已。它
可以大致被描述为按照规律的间隔(通常是以年度为循环周期)来进行的
旅行，可能会涉及一个种群的许多成员，而且仅仅是在完成了长途跋
涉之后才能获得回报。这种行为显示出了遗传的本能。生物学家
Hugh Dingle总结出了五条在不同程度上或以不同组合方式，适用于
所有迁徙行为的特点。迁徙是旷日持久的长距离运动，将动物们带离
熟悉的栖息地;它们往往是沿直线进行，而不是曲折迂回的;它们牵涉到
一些与行前准备(例如超量进食)和到达有关的特殊行为;它们需要进行
特殊的能量分配。并且还有一样：迁徙中的动物有着一种对更远大使
命的格外专注，这使它们不会被任何诱惑转移了注意力，也不会因为
任何会让其他动物望而却步的挑战而裹步不前。
一只北极燕鸥，在它从南美洲的最南端飞向北极圈的20,000公里
途中，对于一个观鸟者从小船上提供给它的一条散发浓烈气味的美味
鲱鱼将会毫不在意。本地海鸥将会贪婪地俯冲下来争食这般馈赠，而
燕鸥却会继续向前飞去。为什么?北极燕鸥之所以抗拒了这一分神因素，
是因为那时那刻它被一种本能感觉所驱动着，我们人类发现这种感觉
十分令人钦佩：它叫做“更远大的目标”。换言之，它下定决心一定
要到达它的目的地。这只鸟感觉到它可以稍后再进食、休息和交配。
当前它的注意力完全集中在旅程本身上;它的绝对唯一目的就是抵达目
的地。去到北极的某个沙砾遍地的海岸，其他北极燕鸥都集结在了那
里，这将让它达成那个由进化所塑造出来的更远大目标：找到某个地
点、某个时间和一系列环境条件，它可以在其间成功地孵化和养育后
代。
然而迁徙是个极其复杂的事件，而生物学家们对它的定义也各有
不同，在某种程度上要取决于他们研究的是何种动物。蒙大纳大学的
Joel Berger研究的是美洲叉角羚和其他大型陆生哺乳动物，他倾向于
使用一个适用于他所研究动物类型的、被他称作简单实用的定义：
“从某个季节性栖息区域去到另一个栖息区域然后再回来的往复运
动”。这种季节性来回移动的原因通常是为了寻找某些在任何一个区
域内都并非全年存在的资源。
但是海洋中浮游生物的每日垂直运动——夜里上浮以寻找食物，
白天下潜以躲避捕食者——也可以被视作迁徒。蚜虫的活动也可被认
为是迁徙：当一株食用植物上的所有嫩叶都被吃光以后，它们的后代
就会飞去另一株宿主植物，没有任何一只蚜虫会回到自己出发的地方
去。
Dingle是位研究昆虫的进化生物学家。他的定义比Berger的定义
更为细致，列举出了将迁徙行为区别于其他形式动物活动的五条特征。
它们考虑到了存在这样的事实情况，例如蚜虫在应该起身踏上它们大
行程的时候会对蓝光(来自天空)变得敏感，而在应该下落的时候则对黄
光(来自嫩叶的反射)敏感。鸟类在进行长途迁徙飞行之前会大量进食来
为自身增脂。(也就是说，Dingle承认每个物种的迁徙行为都存在自身
独特之处而彼此各有差异。)Dingle认为，他所下定义的价值在于，它
集中关注了角马迁徙与蚜虫迁徙现象的共性，并以此来帮助研究者理
解进化是如何导致所有这些共性的产生的。
然而，人类活动正在对动物迁徙产生着有害影响。叉角羚虽然看
起来颇似羚羊，但其实二者并无关系，它是新世界(注：New World
是英国人对美洲大陆的旧称;相应地，英美对传统欧洲国家则称之为
Old World)里速度最快的陆生哺乳动物。其中一个种群会在美国西部
大提顿国家公园的山脉间度过夏天，然后从其山间的夏季牧场沿一条
狭窄路径南下，穿过一条河，最后来到平原上。它们在这里熬过最寒
冷的几个月，主要靠吃被风吹露出雪面以上的灌木蒿丛度日。这些叉
角羚之所以引人注目，在于它们迁徙路线的年复一年从不改变，并且
这条路线在三个瓶颈隘口，狭窄难行。如果它们在春季迁徙的过程中
不能通过这三个路口中的任何一个，就无法抵达它们水草丰美的夏季
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