IELTS Real Reading Test 2025 - Q2 Test 1 with Practice Test, Answers And Explanation
Luyện tập đề IELTS Real Reading Test 2025 - Q2 Test 1 được lấy từ cuốn sách Real Test 2025 - Q2 với trải nghiệm thi IELTS trên máy và giải thích đáp án chi tiết bằng Linearthinking, kèm answer key và list từ vựng IELTS cần học trong bài đọc.
IELTS Real Reading Test 2025 - Q2 Test 1 with Practice Test, Answers And Explanation
Passage
❓ Câu hỏi passage 1
Question 1 - 5
Complete the notes below.
Choose ONE WORD ONLY from the passage for each answer.
Carnivorous Plants
Darwin’s experiments:
Drosera
- He put insects and small amounts of meat onto leaves and observed what happened.
- He was amazed that one human hair triggered a response.
- He understood why the plant did not respond to
1.
.
Venus Flytrap
- He demonstrated how leaves close and then, for a short period, act like a
2.
.
- He noted the structure of leaves ensures small insects are released.
Biology today:Venus Flytrap
- If insects come into contact with leaf hairs, their movement produces an electric charge.
- The charge enters fluid-filled tunnels, causing
3.
in the cell walls to open.
- Water moves between cells and then the leaf changes from convex to concave, trapping the insect inside.
Bladderwort
- Hairs bend when insects swim past, resulting in opening of a flap.
- Water is sucked in.
- When water is pumped out of bladder cells, a
4.
builds up inside.
Pitcher Plants
- The plants have tube-shaped leaves that insects fall into.
- Some plants are big enough to capture and eat
5.
.
Question 6 - 13
Do the following statements agree with the information given in the Reading Passage?
TRUE if the statement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if it is impossible to say what the writer thinks about this
6
Pitcher plants increase in size after they have digested a lot of insects.
7
Carnivorous plants produce light-harvesting enzymes with the nutrients they extract from animals.
8
Pitcher plants and Venus flytraps are more efficient at photosynthesis than plants with ordinary leaves.
9
Venus flytraps are better adapted to the soil of swamps and bogs than other carnivorous plants.
10
Carnivorous plants frequently find it difficult to photosynthesise in bogs due to a lack of sunlight.
11
Scientists have campaigned to reduce the amount of nitrogen that is released into the soil by agricultural practices.
12
A lot of exotic carnivorous plants are sold illegally.
13
Preventing wildfires is beneficial to the Venus flytrap.
Passage
❓ Câu hỏi passage 2
Question 14 - 18
Reading Passage has eleven paragraphs A-K
Which paragraph contains the following information?
Write the correct letter, A-K NB You may use any letter more than once.
14
Mentioned research conducted in Ohio
15
A medical contribution to the researches for twins
16
A research situation under life-threatening conditions
17
Data of similarities of identical twins
18
The reasons that make one study unconvincing
Question 19 - 20
Complete the notes below.
Choose NO MORE THAN TWO WORDS OR A NUMBER from the passage for each answer.
The first one that conducted research on twins is called
19.
. He separated twins into two categories: non-identical and identical twins. The twin research was used in a medical application in as early as the year of
20.
.
Question 21 - 23
Choose THREE letters, A-F.
Please choose THREE research fields that had been carried out in Ohio, Maryland and Twinburgh?
A
Sense
B
Cancer
C
Be allergic to Vitamin D
D
Mole heredity
E
Sound
F
Baldness of men
Question 24 - 26
Choose THREE letters, A-F.
Please choose THREE results that had been verified in this passage.
A
Non-identical twins come from different eggs.
B
Genetic relation between identical twins is closer than non-identical ones.
C
Vitamin C has an evident effect on a cold.
D
Genetic influence on smoking is superior to the environment’s.
E
If a pregnant woman eats too much sweet would lead to skin disease.
F
Hair loss has been found to be connected with a skin problem.
Passage
❓ Câu hỏi passage 3
Question 27 - 30
Choose the correct letter, A, B, C or D.
Write the correct letter in boxes on your answer sheet.
27
Why were the inhabitants of De Smet in danger of starvation?
A
The trains were unable to operate normally.
B
The harvest had been completely destroyed.
C
The roads to the town had not yet been built.
D
The farmers were reluctant to sell their produce.
28
What problem did subsistence farmers have in the past?
A
They had no effective means of storing food.
B
Food was expensive because of high shipping costs.
C
Their access to food was limited at certain times.
D
Food could not be transported for long distances by road.
29
The writer says that the use of coal to power railways and steamships
A
led to a greater range of fresh vegetables being available in urban areas.
B
was less efficient than the use of petroleum-derived products.
C
allowed farmers to be more self-sufficient than they were previously.
D
was better for the environment than using petroleum-derived products.
30
The writer refers to an urban planning conference held in 1898 in order to
A
illustrate a problem that was later solved by modern technology.
B
give an example of poor decisions made about urban planning.
C
show that urban issues were misunderstood in the past.
D
indicate the disregard at the time for public health concerns.
Question 31 - 35
Complete the summary using the list of words, A-J, below.
Write the correct letter, A-J, in boxes on your answer sheet.
Problems caused by urban workhorses
In cities, the large amounts of horse manure led to in the streets and was also linked to the spread of . In certain situations, the horses might even cause to passers-by. There were also the problems of noise and congestion caused by horse-drawn vehicles. In the countryside, there were problems too. The was damaged because of the need to provide for urban workhorses.
A
rich landowners
B
injuries
C
food
D
accidental falls
E
dangerous area
F
use of irrigation
G
environment
H
unpleasant smells
I
treatment
J
diseases
Question 36 - 40
Do the following statements agree with the information given in Reading Passage?
In following statements below, choose
YES if the statement agrees with the information
NO if the statement contradicts the information
NOT GIVEN if it is impossible to say what the writer thinks about this
36
Farmers whose land was poor failed to benefit from modern forms of transport.
37
Between 1830 and 1960 there were positive effects associated with changing patterns of agriculture in France.
38
A fairer distribution of the world's water resources is needed.
39
Living in the countryside does less harm to the environment than living in a city.
40
lt is possible that modern developments in transportation have had a beneficial impact on the world.
DOL IELTS Đình Lực
05/05/2026
📖 Bài đọc passage 1
Carnivorous plant
They attract insects and then eat their flesh. Is that any way for a plant to behave?
The naturalist and author of Origin of Species, Charles Darwin, was fascinated by carnivorous plants. In 1860, soon after he came across his first carnivorous plant — the sundew, Drosera — he wrote, ‘I care more about Drosera than the origin of all the species in the world.’ He spent months running experiments on the plants. He dropped flies and bits of meat on their leaves and watched them slowly fold their sticky tentacles over their prey. He thought it incredible that brushing a leaf with a single strand of human hair was enough to bring about a response. Yet sundews, he observed, ignored raindrops. To react to such a false alarm, he reasoned, would obviously be a great evil to the plant. This was no accident. This was adaptation.
Darwin expanded his studies from sundews to other species in his book Insectivorous Plants. He was amazed at the quickness and power of the Venus flytrap. He showed that when one of its leaves snapped shut, it formed itself into a temporary ‘stomach’, secreting enzymes that could dissolve the prey. He noted that a leaf took more than a week to reopen after closing, and reasoned that the interlocking spines along the margin of the leaf allowed tiny insects to escape, saving the plant the expense of digesting an insufficient meal.
Today, biologists using 21st-century tools to study cells and DNA are beginning to understand how these plants hunt, eat, and digest — and how these strange adaptations came about in the first place. Alexander Volkov, a plant physiologist at Oakwood University in Alabama, believes he has figured out the Venus flytrap’s secret. ‘This,’ Volkov declares, ‘is an electrical plant.’
When an insect brushes against a hair on the leaf of a Venus flytrap, the movement sets off an electric charge. The charge builds up inside the tissue of the leaf but is not enough to stimulate the snap, which keeps the Venus flytrap from reacting to false alarms, such as raindrops. An insect, however, is likely to brush a second hair, adding enough electric charge for the leaf to close.
Volkov’s experiments reveal that the electric charge travels down fluid-filled tunnels in a leaf, which opens up pores in cell membranes. Water rushes from the cells on the inside of the leaf to those on the outside, causing the leaf to rapidly flip in shape from convex to concave, like a soft contact lens. As the leaves flip, they snap together, trapping an insect inside.
The bladderwort plant has an equally sophisticated way of setting its underwater trap. It pumps water out of tiny air sacs or bladders, lowering the pressure inside. When a water flea or some other small creature swims past, it bends hairs on the bladder, causing a flap to spring apart. The low pressure sucks water in, carrying the creature along with it. In one five-hundredth of a second, the flap swings shut again. The cells in the bladder then begin to pump water out again, creating a new vacuum. Many other species of carnivorous plants act like living flypaper, catching animals on sticky tentacles. Pitcher plants use yet another strategy, growing long tube-shaped leaves into which insects fall. Some of the largest have pitchers up to 30cm deep and can consume whole frogs unlucky enough to fall into them. Sophisticated chemistry helps make the pitcher a death trap.
Nicholas Gotelli, of the University of Vermont, is trying to figure out what evolutionary forces pushed these plants towards meat. Carnivorous plants clearly benefit from eating animals; when scientists feed pitcher plants extra bugs, the plants get bigger. But the benefits of eating flesh are not the ones you might expect. Carnivorous animals, like ourselves, use the carbon in protein and the fat in meat to build muscles and store energy. Carnivorous plants, however, take nitrogen and phosphorus from the flesh in order to build light-harvesting enzymes. Eating animals, in other words, lets carnivorous plants do what all plants do: grow by taking energy directly from the sun.
Unfortunately, they do a really bad job of it. That’s because they have to use a lot of energy to make the equipment they need to catch animals — the enzymes, the pumps, the sticky tentacles, and so on. A pitcher or a flytrap is not very good at photosynthesis because, unlike plants with ordinary leaves, they do not have flat solar panels that can absorb lots of sunlight. Gotelli suspects that only under special conditions are the benefits of being carnivorous greater than the costs. The poor soil of bogs and swamps, where many carnivorous plants grow, offers little nitrogen and phosphorus, so carnivorous plants enjoy an advantage there over ‘conventional’ plants. Also, bogs are often flooded with sunshine, so even an inefficient carnivorous plant can carry out enough photosynthesis to survive. ‘They’re stuck, and they’re making the best of it,’ says Aaron Ellison of Harvard University.
Unfortunately, the adaptations that enable carnivorous plants to survive in harsh habitats also make them extremely sensitive to environmental changes. Chemical fertilizers used in agriculture and pollution from power plants are adding extra nitrogen to many bogs in North America. Carnivorous plants are so finely adapted to low levels of nitrogen that this extra fertilizer is overloading their systems. Humans also threaten carnivorous plants in other ways. The black market trade in exotic carnivorous plants is strong, but even if this can be prevented, carnivorous plants will continue to suffer from other dangers. Their habitat is disappearing, to be replaced by shopping centers and houses. The suppression of wildfires by government agencies allows other plants to grow quickly and outcompete the Venus flytraps. Good news, perhaps, for flies. But a loss for all who delight in the inventiveness of evolution.
🔥 Đáp án & giải thích 1
1
raindrops
Giải thích chi tiết
☺️ Ứng dụng Linearthinking để giải quyết dạng bài Gap Fill
Step 01: Read the question to understand (main idea + detail) + Predict Word Form + Meaning
Simplified: the plant did not respond to _____
Prediction: Từ cần điền là danh từ số nhiều(N) → chỉ một hiện tượng mà cây không phản ứng.
-------
Step 02: Locate relevant information
🔍 Từ khoá: “plant”, “did not respond/ignored”
=> Dựa vào các từ khoá trên -> Tìm được trích dẫn ở đoạn 1.
-------
Step 03: Read relevant information to understand (main + detail)
📌 Trích dẫn: "Yet sundews, he observed, ignored raindrops. To react to such a false alarm, he reasoned, would obviously be a great evil to the plant."
Simplified: sundews ignored raindrops → reacting would be harmful
Main idea: Cây gọng vó không phản ứng với những giọt mưa vì đó chỉ là tín hiệu giả và sẽ gây hại nếu phản ứng.
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Step 04: Compare meaning with meaning
Trong bài đọc: Cây bỏ qua các giọt mưa vì phản ứng với chúng sẽ gây hại cho cây.
A. The scientific study of twins goes back to the late 19th century, when Francis Galton, an early geneticist, realised that they came in two varieties: identical twins born from one egg and non-identical twins that had come from two. That insight turned out to be key, although it was not until 1924 that it was used to formulate what is known as the twin rule of pathology, and twin studies really got going.
B
The twin rule of pathology states that any heritable disease will be more concordant (that is, more likely to be jointly present or absent) in identical twins than in non-identical twins – and, in turn, will be more concordant in non-identical twins than in non-siblings. Early work, for example, showed that the statistical correlation of skin-mole counts between identical twins was 0.4, while non-identical twins had a correlation of only 0.2 (a score of 1.0 implies a perfect correlation, while a score of zero implies no correlation.) This result suggests that moles are heritable, but it also implies that there is an environmental component to the development of moles, otherwise, the correlation in identical twins would be close to 1.0.
C
Twin research has shown that whether or not someone takes up smoking is determined mainly by environmental factors, but once he does so, how much he smokes is largely down to his genes. And while a person’s religion is clearly a cultural attribute, there is a strong genetic component to religious fundamentalism. Twin studies are also unraveling the heritability of various aspects of human personality. Traits from neuroticism and anxiety to thrill – and novelty-seeking all have large genetic components. Parenting matters, but it does not determine personality in the way that some had thought.
D
More importantly, perhaps, twin studies are helping the understanding of diseases such as cancer, asthma, osteoporosis, arthritis and immune disorders. And twins can be used, within ethical limits, for medical experiments. A study that administered vitamin C to one twin and a placebo to the other found that it had no effect on the common cold. The lesson from all of today’s twin studies is that most human traits are at least partially influenced by genes. However, for the most part, the age-old dichotomy between nature and nurture is not very useful. Many genetic programs are open to input from the environment, and genes are frequently switched on or off by environmental signals. It is also possible that genes themselves influence their environment. Some humans have an innate preference for participation in sports. Others are drawn to novelty. Might people also be drawn to certain kinds of friends and types of experience? In this way, a person’s genes might shape the environment they act in as much as the environment shapes the actions of the genes.
E
In the past, such research has been controversial. Josef Mengele, a Nazi doctor working at the Auschwitz extermination camp during the second world war, was fascinated by twins. He sought them out among arrivals at the camp and preserved them from the gas-chambers for a series of brutal experiments. After the war, Cyril Burt, a British psychologist who worked on the heredity of intelligence, tainted twin research with results that appear, in retrospect, to have been rather too good. Some of his data on identical twins who had been reared apart were probably faked. In any case, the prevailing ideology in the social sciences after the war was Marxist and disliked suggestions that differences in human potential might have underlying genetic causes. Twin studies were thus viewed with suspicion.
F
The ideological pendulum has swung back; however, as the human genome project and its aftermath have turned genes for abstract concepts to real pieces of DNA. The role of genes in sensitive areas such as intelligence is acknowledged by all but a few die-hards. The interesting questions now concern how nature and nurture interact to produce particular bits of biology, rather than which of the two is more important. Twin studies, which are a good way to ask these questions, are back in fashion, and many twins are enthusiastic participants in this research.
G
Research at the Twinsburg festival began in a small way, with a single stand in 1979. Gradually, news spread and more scientists began turning up. This year, half a dozen groups of researchers were lodged in a specially pitched research tent. In one corner of this tent, Paul Breslin, who works at the Monell Institute in Philadelphia, watched over several tables where twins sat sipping clear liquids from cups and making notes. It was the team’s third year at Twinsburg. Dr Breslin and his colleagues want to find out how genes influence human perception, particularly the senses of smell and taste and those (warmth, cold, pain, tingle, itch and so on) that result from stimulation of the skin. Perception is an example of something that is probably influenced by both genes and experience. Even before birth, people are exposed to flavours such as chocolate, garlic, mint and vanilla that pass intact into the bloodstream, and thus to the fetus. Though it is not yet clear whether such pre-natal exposure shapes taste-perception, there is evidence that it shapes preferences for foods encountered later in life.
H
However, there are clearly genetic influences at work, as well – for example in the ability to taste quinine. Some people experience this as intensely bitter, even when it is present at very low levels. Others, whose genetic endowment is different, are less bothered by it. Twin studies make this extremely clear. Within a pair of identical twins, either both, or neither, will find quinine hard to swallow. Non-identical twins will agree less frequently.
I
On the other side of the tent, Dennis Drayna, from the National Institute on Deafness and Other Communication Disorders, in Maryland, was studying hearing. He wants to know what happens to sounds after they reach the ear. It is not clear, he says, whether the sound is processed into sensation mostly in the ear or in the brain. Dr Drayna has already been involved in a twin study which revealed that the perception of musical pitch is highly heritable. At Twinsburg, he is playing different words, or parts of words, into the left and right ears of his twinned volunteers. The composite of the two sounds that an individual reports hearing depends on how he processes this diverse information and that, Dr Drayna believes, may well be influenced by genetics.
J
Elsewhere in the marquee, Peter Miraldi, of Kent State University in Ohio, was trying to find out whether genes affect an individual’s motivation to communicate with others. A number of twin studies have shown that personality and sociability are heritable, so he thinks this is fertile ground. And next to Mr Miraldi was a team of dermatologists from Case Western Reserve University in Cleveland. They are looking at the development of skin disease and male-pattern baldness. The goal of the latter piece of research is to find the genes responsible for making men’s hair fall out.
K
The busiest part of the tent, however, was the queue for forensic-science research into fingerprints. The origins of this study are shrouded in mystery. For many months, the festival’s organisers have been convinced that the Secret Service – the American government agency responsible for, among other things, the safety of the president – is behind it. When The Economist contacted the Secret Service for more information, we were referred to Steve Nash, who is chairman of the International Association for Identification (IAI) and is also a detective in the scientific investigations section of the Marin Country Sheriff’s Office in California. The IAI, based in Minnesota, is an organisation of forensic scientists from around the world. Among other things, it publishes the Journal of Forensic Identification.
🔥 Đáp án & giải thích 2
14
J
Giải thích chi tiết
☺️ Ứng dụng Linearthinking để giải quyết dạng bài Matching Information
📌 Dạng Matching Information chúng ta nên làm cuối cùng, sau khi đã làm các dạng câu hỏi khác nhé DOLBIES, bởi vì lúc này mình đã đọc và hiểu nội dung của bài rồi, cộng thêm nghệ thuật Specify của Linearthinking → sẽ nhanh chóng tìm được vị trí đáp án hơn!!
-------
Step 01: Read the question to predict
Hiểu câu hỏi: Mentioned research conducted in Ohio
Specify & Predict: Đoạn văn sẽ đưa thông tin chi tiết hơn về một/ vài nhóm nghiên cứu và địa điểm ở Ohio (tên trường/ thành phố) nơi họ đang tiến hành nghiên cứu.
-------
Step 02: Khoanh vùng đoạn văn
🔍 Từ khóa: “research", "conducted in Ohio"
→ Dựa vào các từ khoá trên, có thể khoanh vùng được đoạn J vì có xuất hiện các cụm như:
"Kent State University in Ohio" (Đại học Kent State ở Ohio - địa điểm thực hiện);
"trying to find out whether genes affect" (cố gắng tìm hiểu xem liệu gen có ảnh hưởng - mô tả hoạt động "research");
"Cleveland" (một thành phố khác thuộc bang Ohio).
→ Đây là ví dụ cụ thể cho "Mentioned research conducted in Ohio".
Laura Ingalls Wilder's semi-autobiographical novel The Long Winter describes how the inhabitants of a small town called De Smet in the American mid-west narrowly avoided starvation during the severe winter of 1880-1881. Over three metres of snow fell on the northern plains, immobilising the railways and cutting off the settlers from the rest of the world. Laura and her neighbours were only saved when her fiancé and his friend trudged 30 kilometres through the snow to fetch food, risking their lives in the process. The story is a reminder of how lethal geographical isolation and crop failures could be before the advent of modern farming and transportation technologies. Not long ago, subsistence farmers in many countries had to cope with the 'lean season' – the period of greatest scarcity before new crops became available. In England, late spring was once referred to as the 'hungry gap'. The situation was made worse by the cost of moving heavy things over muddy dirt roads; three centuries ago, moving goods 50 kilometres on land between, say, Liverpool and Manchester was as expensive as shipping them across the north Atlantic.
The development of coal-powered railways and steamships in the 19th century revolutionized the lives of farmers. Instead of having to grow everything they needed, they could now specialise in what they did best and rely on other producers for their remaining needs. The result was not only food and ever-cheaper prices, but the end of widespread famine and starvation, as the surplus from regions with good harvests could now be transported to those that had experienced mediocre ones. Since then, petroleum-derived fuels have largely displaced coal because of their higher energy density, cleaner combustion and greater ease of extraction, further improving road and rail transportation systems.
While the convenience of modern methods of transportation is obvious, few people grasp their historical significance in terms of their beneficial impact on large cities and the health of residents. In 1898, delegates gathered in New York City for the world's first international urban-planning conference: The topic that dominated discussions was not infrastructure or housing, but horse manure. The problem was that as the populations of cities like New York and London grew, the number of horses there also grew, and in New York these produced nearly two million kilograms of manure each day. If this problem continued it was estimated that by 1950 every street in London would be buried three metres deep in horse manure. Unable to think of any solution, the delegates concluded that urban living was inherently unsustainable.
Paradoxically, much of the urban manure problem was related to the growth of the railways. The ability to deliver perishable goods, such as meat and dairy products, from locations that benefited from better soil and climate, put many farms located near cities out of business. As these had relied on manure from city workhorses for fertilizer, the demand for this was greatly reduced.
The impact of urban workhorses was felt both in the cities and in the countryside. In cities, apart from their overpowering stench, the manure piles were prime breeding grounds for house flies, perhaps three billion of which hatched each day in US cities in the early 20th century. With flies came outbreaks of typhoid, cholera and diphtheria. Workhorses sometimes panicked in heavy traffic and kicked or bit bystanders. The clatter of wagon wheels on cobblestone pavement could be deafening, and since a horse and wagon occupied more street space than a modern truck, they also created significant traffic congestion, while a horse that collapsed on the road created an obstruction that was difficult to remove. The countryside also suffered. To supply the workhorses with oats and hay, additional land had to be cleared of its natural animal life and vegetation, and sometimes water had to be diverted to irrigate it, with considerable negative effects on the whole area.
So, while the trains, cars and trucks of the early 20th century were noisy and polluting by today's standards, they were regarded as a significant improvement on what had gone before. Before they were available, poor soils often meant that a large amount of land was required to sustain a household, and much environmental damage, primarily in the form of soil erosion, was caused by trying to farm these soils. It could be argued that modern transportation allowed the development of remote regions like the Canadian prairies and allowed more suitable crops to be grown in the poorer soils in Europe before being sold elsewhere.
Over time, the concentration of food production in the world's best locations allowed some agricultural land to revert to a wild state. For instance, France benefited from an expansion of its forest area by one third between 1830 and 1960. This so-called 'forest transition' occurred in the context of a doubling of the French population and a dramatic increase in standards of living. Improvements in logistics also allowed the production and export of food from locations where water was abundant to regions where it was scarce, thus preventing the depletion of water resources there. It also made possible a drastic increase in the size of our cities. Contrary to what most people believe, the growth in cities is a positive development. In the words of economist Ed Glaser: 'Residing in a forest might seem to be a good way of showing one's love of nature, but living in a concrete jungle is actually far more ecologically friendly... . If you love nature, stay away from it. It could be argued that modern transportation technologies have been a major contributor to a wealthier, cleaner and more sustainable world.'
🔥 Đáp án & giải thích 3
27
A
Giải thích chi tiết
☺️ Ứng dụng Linearthinking để giải quyết dạng bài Multiple Choice
Step 01: Read the question to understand (main idea + detail)
Simplified: Why the inhabitants of De Smet were in danger of starvation
Main idea: Câu hỏi yêu cầu xác định nguyên nhân trực tiếp khiến người dân De Smet đối mặt với nguy cơ chết đói.
-------
Step 02: Locate relevant information
🔍 Từ khoá: “De Smet”, “starvation”, “trains”, “harvest“, “roads”, ”farmers”
=> Dựa vào các từ khoá trên -> Tìm được trích dẫn ở đoạn 1.
-------
Step 03: Read relevant information to understand (main + detail)
📌 Trích dẫn: “Over three metres of snow fell on the northern plains, immobilising the railways and cutting off the settlers from the rest of the world.”
Simplified: over three metres of snow fell -> immobilising the railways and cutting off the settlers from the rest of the world => không thể tiếp cận nguồn lương thực → nguy cơ chết đói
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Step 04: Compare meaning with meaning
✅ A. The trains were unable to operate normally.: khớp trực tiếp với “immobilising the railways” → tàu hoả không thể vận hành, khiến thị trấn bị cô lập.
❌ B. The harvest had been completely destroyed.: đoạn không đề cập đến mùa màng bị phá huỷ, mà là vấn đề vận chuyển.
❌ C. The roads to the town had not yet been built.: không nói đến việc chưa có đường; nguyên nhân là tuyết làm tê liệt hệ thống hiện có.
❌ D. The farmers were reluctant to sell their produce.: không có thông tin nào về thái độ của nông dân; đây là suy diễn ngoài bài.
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✅ Đáp án: A. The trains were unable to operate normally.
The naturalist and author of Origin of Species, Charles Darwin, was fascinated by carnivorous plants. In 1860, soon after he came across his first carnivorous plant — the sundew, Drosera — he wrote, ‘I care more about Drosera than the origin of all the species in the world.’ He spent months running experiments on the plants. He dropped flies and bits of meat on their leaves and watched them slowly fold their sticky tentacles over their prey. He thought it incredible that brushing a leaf with a single strand of human hair was enough to bring about a response. Yet sundews, he observed, ignored raindrops. To react to such a false alarm, he reasoned, would obviously be a great evil to the plant. This was no accident. This was adaptation.
Darwin expanded his studies from sundews to other species in his book Insectivorous Plants. He was amazed at the quickness and power of the Venus flytrap. He showed that when one of its leaves snapped shut, it formed itself into a temporary ‘stomach’, secreting enzymes that could dissolve the prey. He noted that a leaf took more than a week to reopen after closing, and reasoned that the interlocking spines along the margin of the leaf allowed tiny insects to escape, saving the plant the expense of digesting an insufficient meal.
Today, biologists using 21st-century tools to study cells and DNA are beginning to understand how these plants hunt, eat, and digest — and how these strange adaptations came about in the first place. Alexander Volkov, a plant physiologist at Oakwood University in Alabama, believes he has figured out the Venus flytrap’s secret. ‘This,’ Volkov declares, ‘is an electrical plant.’
When an insect brushes against a hair on the leaf of a Venus flytrap, the movement sets off an electric charge. The charge builds up inside the tissue of the leaf but is not enough to stimulate the snap, which keeps the Venus flytrap from reacting to false alarms, such as raindrops. An insect, however, is likely to brush a second hair, adding enough electric charge for the leaf to close.
Volkov’s experiments reveal that the electric charge travels down fluid-filled tunnels in a leaf, which opens up pores in cell membranes. Water rushes from the cells on the inside of the leaf to those on the outside, causing the leaf to rapidly flip in shape from convex to concave, like a soft contact lens. As the leaves flip, they snap together, trapping an insect inside.
The bladderwort plant has an equally sophisticated way of setting its underwater trap. It pumps water out of tiny air sacs or bladders, lowering the pressure inside. When a water flea or some other small creature swims past, it bends hairs on the bladder, causing a flap to spring apart. The low pressure sucks water in, carrying the creature along with it. In one five-hundredth of a second, the flap swings shut again. The cells in the bladder then begin to pump water out again, creating a new vacuum. Many other species of carnivorous plants act like living flypaper, catching animals on sticky tentacles. Pitcher plants use yet another strategy, growing long tube-shaped leaves into which insects fall. Some of the largest have pitchers up to 30cm deep and can consume whole frogs unlucky enough to fall into them. Sophisticated chemistry helps make the pitcher a death trap.
Nicholas Gotelli, of the University of Vermont, is trying to figure out what evolutionary forces pushed these plants towards meat. Carnivorous plants clearly benefit from eating animals; when scientists feed pitcher plants extra bugs, the plants get bigger. But the benefits of eating flesh are not the ones you might expect. Carnivorous animals, like ourselves, use the carbon in protein and the fat in meat to build muscles and store energy. Carnivorous plants, however, take nitrogen and phosphorus from the flesh in order to build light-harvesting enzymes. Eating animals, in other words, lets carnivorous plants do what all plants do: grow by taking energy directly from the sun.
Unfortunately, they do a really bad job of it. That’s because they have to use a lot of energy to make the equipment they need to catch animals — the enzymes, the pumps, the sticky tentacles, and so on. A pitcher or a flytrap is not very good at photosynthesis because, unlike plants with ordinary leaves, they do not have flat solar panels that can absorb lots of sunlight. Gotelli suspects that only under special conditions are the benefits of being carnivorous greater than the costs. The poor soil of bogs and swamps, where many carnivorous plants grow, offers little nitrogen and phosphorus, so carnivorous plants enjoy an advantage there over ‘conventional’ plants. Also, bogs are often flooded with sunshine, so even an inefficient carnivorous plant can carry out enough photosynthesis to survive. ‘They’re stuck, and they’re making the best of it,’ says Aaron Ellison of Harvard University.
Unfortunately, the adaptations that enable carnivorous plants to survive in harsh habitats also make them extremely sensitive to environmental changes. Chemical fertilizers used in agriculture and pollution from power plants are adding extra nitrogen to many bogs in North America. Carnivorous plants are so finely adapted to low levels of nitrogen that this extra fertilizer is overloading their systems. Humans also threaten carnivorous plants in other ways. The black market trade in exotic carnivorous plants is strong, but even if this can be prevented, carnivorous plants will continue to suffer from other dangers. Their habitat is disappearing, to be replaced by shopping centers and houses. The suppression of wildfires by government agencies allows other plants to grow quickly and outcompete the Venus flytraps. Good news, perhaps, for flies. But a loss for all who delight in the inventiveness of evolution.
B. The twin rule of pathology states that any heritable disease will be more concordant (that is, more likely to be jointly present or absent) in identical twins than in non-identical twins – and, in turn, will be more concordant in non-identical twins than in non-siblings. Early work, for example, showed that the statistical correlation of skin-mole counts between identical twins was 0.4, while non-identical twins had a correlation of only 0.2 (a score of 1.0 implies a perfect correlation, while a score of zero implies no correlation.) This result suggests that moles are heritable, but it also implies that there is an environmental component to the development of moles, otherwise, the correlation in identical twins would be close to 1.0.
C. Twin research has shown that whether or not someone takes up smoking is determined mainly by environmental factors, but once he does so, how much he smokes is largely down to his genes. And while a person’s religion is clearly a cultural attribute, there is a strong genetic component to religious fundamentalism. Twin studies are also unraveling the heritability of various aspects of human personality. Traits from neuroticism and anxiety to thrill – and novelty-seeking all have large genetic components. Parenting matters, but it does not determine personality in the way that some had thought.
D. More importantly, perhaps, twin studies are helping the understanding of diseases such as cancer, asthma, osteoporosis, arthritis and immune disorders. And twins can be used, within ethical limits, for medical experiments. A study that administered vitamin C to one twin and a placebo to the other found that it had no effect on the common cold. The lesson from all of today’s twin studies is that most human traits are at least partially influenced by genes. However, for the most part, the age-old dichotomy between nature and nurture is not very useful. Many genetic programs are open to input from the environment, and genes are frequently switched on or off by environmental signals. It is also possible that genes themselves influence their environment. Some humans have an innate preference for participation in sports. Others are drawn to novelty. Might people also be drawn to certain kinds of friends and types of experience? In this way, a person’s genes might shape the environment they act in as much as the environment shapes the actions of the genes.
E. In the past, such research has been controversial. Josef Mengele, a Nazi doctor working at the Auschwitz extermination camp during the second world war, was fascinated by twins. He sought them out among arrivals at the camp and preserved them from the gas-chambers for a series of brutal experiments. After the war, Cyril Burt, a British psychologist who worked on the heredity of intelligence, tainted twin research with results that appear, in retrospect, to have been rather too good. Some of his data on identical twins who had been reared apart were probably faked. In any case, the prevailing ideology in the social sciences after the war was Marxist and disliked suggestions that differences in human potential might have underlying genetic causes. Twin studies were thus viewed with suspicion.
F. The ideological pendulum has swung back; however, as the human genome project and its aftermath have turned genes for abstract concepts to real pieces of DNA. The role of genes in sensitive areas such as intelligence is acknowledged by all but a few die-hards. The interesting questions now concern how nature and nurture interact to produce particular bits of biology, rather than which of the two is more important. Twin studies, which are a good way to ask these questions, are back in fashion, and many twins are enthusiastic participants in this research.
G. Research at the Twinsburg festival began in a small way, with a single stand in 1979. Gradually, news spread and more scientists began turning up. This year, half a dozen groups of researchers were lodged in a specially pitched research tent. In one corner of this tent, Paul Breslin, who works at the Monell Institute in Philadelphia, watched over several tables where twins sat sipping clear liquids from cups and making notes. It was the team’s third year at Twinsburg. Dr Breslin and his colleagues want to find out how genes influence human perception, particularly the senses of smell and taste and those (warmth, cold, pain, tingle, itch and so on) that result from stimulation of the skin. Perception is an example of something that is probably influenced by both genes and experience. Even before birth, people are exposed to flavours such as chocolate, garlic, mint and vanilla that pass intact into the bloodstream, and thus to the fetus. Though it is not yet clear whether such pre-natal exposure shapes taste-perception, there is evidence that it shapes preferences for foods encountered later in life.
H. However, there are clearly genetic influences at work, as well – for example in the ability to taste quinine. Some people experience this as intensely bitter, even when it is present at very low levels. Others, whose genetic endowment is different, are less bothered by it. Twin studies make this extremely clear. Within a pair of identical twins, either both, or neither, will find quinine hard to swallow. Non-identical twins will agree less frequently.
I. On the other side of the tent, Dennis Drayna, from the National Institute on Deafness and Other Communication Disorders, in Maryland, was studying hearing. He wants to know what happens to sounds after they reach the ear. It is not clear, he says, whether the sound is processed into sensation mostly in the ear or in the brain. Dr Drayna has already been involved in a twin study which revealed that the perception of musical pitch is highly heritable. At Twinsburg, he is playing different words, or parts of words, into the left and right ears of his twinned volunteers. The composite of the two sounds that an individual reports hearing depends on how he processes this diverse information and that, Dr Drayna believes, may well be influenced by genetics.
J. Elsewhere in the marquee, Peter Miraldi, of Kent State University in Ohio, was trying to find out whether genes affect an individual’s motivation to communicate with others. A number of twin studies have shown that personality and sociability are heritable, so he thinks this is fertile ground. And next to Mr Miraldi was a team of dermatologists from Case Western Reserve University in Cleveland. They are looking at the development of skin disease and male-pattern baldness. The goal of the latter piece of research is to find the genes responsible for making men’s hair fall out.
K. The busiest part of the tent, however, was the queue for forensic-science research into fingerprints. The origins of this study are shrouded in mystery. For many months, the festival’s organisers have been convinced that the Secret Service – the American government agency responsible for, among other things, the safety of the president – is behind it. When The Economist contacted the Secret Service for more information, we were referred to Steve Nash, who is chairman of the International Association for Identification (IAI) and is also a detective in the scientific investigations section of the Marin Country Sheriff’s Office in California. The IAI, based in Minnesota, is an organisation of forensic scientists from around the world. Among other things, it publishes the Journal of Forensic Identification.
Laura Ingalls Wilder's semi-autobiographical novel The Long Winter describes how the inhabitants of a small town called De Smet in the American mid-west narrowly avoided starvation during the severe winter of 1880-1881. Over three metres of snow fell on the northern plains, immobilising the railways and cutting off the settlers from the rest of the world. Laura and her neighbours were only saved when her fiancé and his friend trudged 30 kilometres through the snow to fetch food, risking their lives in the process. The story is a reminder of how lethal geographical isolation and crop failures could be before the advent of modern farming and transportation technologies. Not long ago, subsistence farmers in many countries had to cope with the 'lean season' – the period of greatest scarcity before new crops became available. In England, late spring was once referred to as the 'hungry gap'. The situation was made worse by the cost of moving heavy things over muddy dirt roads; three centuries ago, moving goods 50 kilometres on land between, say, Liverpool and Manchester was as expensive as shipping them across the north Atlantic.
The development of coal-powered railways and steamships in the 19th century revolutionized the lives of farmers. Instead of having to grow everything they needed, they could now specialise in what they did best and rely on other producers for their remaining needs. The result was not only food and ever-cheaper prices, but the end of widespread famine and starvation, as the surplus from regions with good harvests could now be transported to those that had experienced mediocre ones. Since then, petroleum-derived fuels have largely displaced coal because of their higher energy density, cleaner combustion and greater ease of extraction, further improving road and rail transportation systems.
While the convenience of modern methods of transportation is obvious, few people grasp their historical significance in terms of their beneficial impact on large cities and the health of residents. In 1898, delegates gathered in New York City for the world's first international urban-planning conference: The topic that dominated discussions was not infrastructure or housing, but horse manure. The problem was that as the populations of cities like New York and London grew, the number of horses there also grew, and in New York these produced nearly two million kilograms of manure each day. If this problem continued it was estimated that by 1950 every street in London would be buried three metres deep in horse manure. Unable to think of any solution, the delegates concluded that urban living was inherently unsustainable.
Paradoxically, much of the urban manure problem was related to the growth of the railways. The ability to deliver perishable goods, such as meat and dairy products, from locations that benefited from better soil and climate, put many farms located near cities out of business. As these had relied on manure from city workhorses for fertilizer, the demand for this was greatly reduced.
The impact of urban workhorses was felt both in the cities and in the countryside. In cities, apart from their overpowering stench, the manure piles were prime breeding grounds for house flies, perhaps three billion of which hatched each day in US cities in the early 20th century. With flies came outbreaks of typhoid, cholera and diphtheria. Workhorses sometimes panicked in heavy traffic and kicked or bit bystanders. The clatter of wagon wheels on cobblestone pavement could be deafening, and since a horse and wagon occupied more street space than a modern truck, they also created significant traffic congestion, while a horse that collapsed on the road created an obstruction that was difficult to remove. The countryside also suffered. To supply the workhorses with oats and hay, additional land had to be cleared of its natural animal life and vegetation, and sometimes water had to be diverted to irrigate it, with considerable negative effects on the whole area.
So, while the trains, cars and trucks of the early 20th century were noisy and polluting by today's standards, they were regarded as a significant improvement on what had gone before. Before they were available, poor soils often meant that a large amount of land was required to sustain a household, and much environmental damage, primarily in the form of soil erosion, was caused by trying to farm these soils. It could be argued that modern transportation allowed the development of remote regions like the Canadian prairies and allowed more suitable crops to be grown in the poorer soils in Europe before being sold elsewhere.
Over time, the concentration of food production in the world's best locations allowed some agricultural land to revert to a wild state. For instance, France benefited from an expansion of its forest area by one third between 1830 and 1960. This so-called 'forest transition' occurred in the context of a doubling of the French population and a dramatic increase in standards of living. Improvements in logistics also allowed the production and export of food from locations where water was abundant to regions where it was scarce, thus preventing the depletion of water resources there. It also made possible a drastic increase in the size of our cities. Contrary to what most people believe, the growth in cities is a positive development. In the words of economist Ed Glaser: 'Residing in a forest might seem to be a good way of showing one's love of nature, but living in a concrete jungle is actually far more ecologically friendly... . If you love nature, stay away from it. It could be argued that modern transportation technologies have been a major contributor to a wealthier, cleaner and more sustainable world.'
fell
immobilising the railways
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cutting off the settlers from the rest of the world
