IELTS Academic Reading Practice Test 50

For centuries, sailors and merchants dreamed of a way to avoid the long, dangerous voyage around Cape Horn. The narrow Isthmus of Panama, joining North and South America, separates the Atlantic and Pacific Oceans by only about eighty kilometres at its narrowest point. As early as the sixteenth century, Spanish officials surveyed possible routes, but the technology of the time could not overcome the dense jungle, the steep hills and the torrential rainfall. For another three hundred years, the idea remained no more than an ambition.

The first serious attempt began in 1881 under Ferdinand de Lesseps, the celebrated French engineer who had built the Suez Canal. Confident after his Egyptian success, de Lesseps initially insisted on a sea-level channel through the isthmus, in which ships would pass without locks. The geography was far more hostile than the flat desert of Suez.

Workers in the damp lowlands faced flash floods, landslips and the constant threat of yellow fever and malaria, whose true causes were not yet understood. By the time the French company collapsed in 1889, around twenty thousand workers had died, and the partly dug canal lay abandoned. De Lesseps raised money from thousands of small investors, and his failure ruined many of them.

The French failure did not end the dream. The United States, which needed a shorter route between its eastern and western coasts, agreed in 1902 to buy the French company's assets, and the purchase was completed two years later. An initial attempt to obtain rights from Colombia, which then ruled Panama, failed, and in 1903 Panama declared independence with United States support. The Hay–Bunau-Varilla Treaty, signed later that year, granted the United States a zone of land across the isthmus in which to build and operate a canal. The agreement also gave the United States the right to intervene in Panamanian affairs. In 1904 work began under American direction, though early progress was slowed by the same tropical diseases that had defeated the French.

The man who tackled that problem was Dr William Gorgas, the chief sanitary officer. Gorgas was convinced that yellow fever and malaria were spread by mosquitoes, an idea that was still controversial among colleagues. He organised teams to drain standing water, cover water containers, spray oil on breeding pools and install screens in buildings. Within a few years, yellow fever had been eliminated from the canal zone and malaria dramatically reduced. The success made large-scale construction possible and influenced public-health campaigns elsewhere.

The other decisive change came from John Stevens, the chief engineer appointed in 1905. Stevens halted digging and concentrated on building the infrastructure needed to support a huge workforce: new housing, mess halls, workshops and a railway that could carry away excavated soil. He also argued that a sea-level canal was impractical, and persuaded the authorities to adopt a design using locks and an artificial lake. Stevens resigned before the project was finished, but his plan was followed by George Goethals, who completed the work.

The construction required tens of thousands of labourers, many of them recruited from the Caribbean islands. They worked in brutal heat and humidity, often in waist-deep water, and were housed in camps that were initially overcrowded. Although the American authorities provided medical care, accidents and disease continued to claim lives throughout the project. The final cost in human life remains difficult to calculate, but it is certain that the canal was built at a heavy price.

The chosen design depended on a huge dam across the Chagres River, which created Gatun Lake, then the largest artificial lake in the world. Rather than cutting a channel all the way down to sea level, engineers raised ships in three stages through locks at Gatun to the lake, and then lowered them again through locks at Pedro Miguel and Miraflores on the Pacific side. The hardest section remained the Culebra Cut, a winding trench through the continental divide where landslips repeatedly filled the excavation and delayed progress for years. Even today, the cut remains one of the most impressive artificial gorges on Earth.

On 15 August 1914 the canal opened, though the event was overshadowed by the outbreak of the First World War. The first complete passage was made by the cargo ship SS Ancon. The finished canal was about eighty kilometres long from deep water to deep water and reduced the voyage from New York to San Francisco by roughly thirteen thousand kilometres. For most ships, the crossing took around ten hours, including time spent in locks. Although the ceremony was low-key because of the war, the opening marked the completion of one of the largest engineering projects in history.

In the following decades, the canal became one of the world's most important waterways, carrying a growing share of global trade. By the early twenty-first century, roughly five per cent of world trade passed through it each year. In 1999 control was transferred to Panama. A major expansion opened in 2016 added a third set of larger locks, allowing much bigger container ships to use the route. The new locks were designed to reduce water consumption, a critical concern in the tropical climate. The canal remains a major source of revenue for the Panamanian economy.

Hibernation is widely assumed to be a long winter sleep, but biologically it is a far more radical state. Hibernation is a condition of greatly reduced activity and metabolism that allows an animal to survive periods when food is scarce and temperatures are low. During the most extreme cases, a hibernating mammal may appear almost lifeless: its body temperature drops close to freezing, its heart beats only a few times a minute, and it breathes so slowly that movement is hard to detect. However, not all animals that are said to hibernate experience such dramatic changes.

True hibernators, such as ground squirrels and marmots, enter a condition known as torpor. In torpor, an animal's core body temperature falls to just above the temperature of its surroundings, and its metabolic rate may drop to less than five per cent of normal. This is not a form of sleep, which is a distinct brain state; instead, the animal is in a profound state of energy conservation. A hibernating ground squirrel can reduce its energy use by more than ninety per cent, surviving for months on the fat stored in its body during the previous summer.

Hibernation is not one continuous state. Many species alternate between periods of torpor lasting days or weeks and short periods of normal temperature. These interruptions are costly, because warming a cold body uses large amounts of stored energy. However, they appear essential for removing waste products, maintaining brain function and, in some cases, allowing genuine sleep. Without periodic arousal, the animal would eventually fail to complete the hibernation cycle.

One of the most remarkable hibernators is the Arctic ground squirrel. During hibernation, this small rodent can lower its body temperature below the freezing point of water without its blood turning to ice. The squirrel achieves this by removing particles around which ice crystals might form, a process known as supercooling. Periodically, however, the animal warms itself back to a normal temperature for several hours, using large amounts of stored energy, before cooling again. Scientists believe these warming episodes may allow the animal to sleep, repair tissues or restore brain function.

Some hibernators do not rely on supercooling but instead take a radically different approach. The wood frog, for example, survives winter by allowing ice to form in spaces outside its cells. Up to two-thirds of the frog's body water may freeze, and the animal's heart and breathing stop completely. High concentrations of glucose produced by the liver act as a natural antifreeze, protecting cells from damage. When the temperature rises in spring, the frog thaws and resumes normal activity within hours.

Not all hibernators are small. The American black bear is often described as a hibernator, although some biologists prefer to call its winter condition a state of winter lethargy or denning. Unlike a ground squirrel, a bear's body temperature falls only slightly, from about 38 to perhaps 31 degrees Celsius, and the animal can be roused relatively easily. Nevertheless, a bear can spend several months without eating, drinking, urinating or defecating, and female bears give birth during this period and nurse their cubs in the den. Bears also recycle urea to build protein and do not lose bone density during their long inactivity.

Research on hibernation has attracted interest from medical scientists. If doctors could safely lower a patient's body temperature and slow their metabolism, they might be able to buy precious time after a stroke or cardiac arrest, when tissues are starved of oxygen. The study of torpor may also help improve techniques for preserving organs for transplant, which currently have to be used very quickly. Several laboratories are investigating the chemical signals that trigger and reverse hibernation in animals, in the hope of eventually applying this knowledge to humans.

However, transferring hibernation to people remains a distant goal. The human body does not appear to possess the natural mechanisms that prevent ice damage or restart organs after long periods of cold. Moreover, animals do not simply switch hibernation on; the process is carefully timed by internal clocks and external cues such as day length and food availability. If any of these signals is missing, the animal may fail to hibernate properly or may wake at the wrong time, with dangerous consequences. Ethical and practical barriers also limit experiments that would be needed to test hibernation in humans.

Nevertheless, studying hibernation offers clues about how animals cope with extreme environments, and how some are responding to climate change. Species that rely on predictable winters are already shifting their ranges or emerging earlier in the spring, sometimes before their food sources are available. Long-term studies of marked animals have revealed that some species now hibernate for shorter periods than they did a few decades ago. Protecting hibernation habitats may prove as important for conservation as preventing direct hunting. In a warming world, understanding the quiet physiology of winter sleepers is becoming an urgent task.

Slang is the most restless part of any language. One generation's fashionable word is the next generation's embarrassment, and dictionaries often record an expression only after its peak has passed. Yet the process by which slang spreads is not random. Sociolinguists have long noted that slang usually begins in a particular social group, often young people in cities, and then travels outward through overlapping networks of friends, schools, workplaces and media. To understand how slang spreads, we need to look at who uses new words, why they use them, and how those words move from a single conversation to general use.

The first stage is innovation. A new word or phrase is coined, or an existing word is given a new meaning. Innovations are rarely deliberate; they arise in everyday talk, often as a way of showing membership in a group or marking a boundary against outsiders. Teenagers are particularly active creators of slang because they are building identities separate from their parents, and because their social groups are tightly knit. A term that becomes popular in one school or neighbourhood may act as a badge of belonging, and those who use it signal that they are part of the same social world. Adults also use slang, but they tend to be slower to adopt new terms.

From these small beginnings, a term may spread if the people who use it have high social prestige or occupy central positions in social networks. Researchers who study social influence have found that innovations do not move purely by geography. Instead, they jump from one city to another when people in different places have regular contact, for example through music, sport or online communities. This explains why a term used in London can appear in Toronto or Lagos before it reaches smaller towns only a short distance from London. Distance matters less than connectedness.

Historically, slang has often been associated with particular subcultures. In the early twentieth century, jazz musicians created a rich vocabulary that later influenced mainstream speech, with words like 'hip' and 'cool'. More recently, hip-hop culture has been a major source of new expressions, spreading them around the world through music and fashion. The movement from subculture to mainstream can take decades, but the same basic channels of face-to-face contact and media exposure operate throughout.

Not every new word survives, of course. The majority of slang terms disappear within a few years, and only a small proportion enter the general vocabulary. Linguists sometimes distinguish between 'slang' and 'general slang' or 'colloquial speech'. A term may become fashionable for a season and then vanish, while a few, such as 'cool' or 'okay', move gradually into standard language. One reason for this difference is usefulness: words that fill a gap in meaning are more likely to last. Another reason is social visibility: a term used by a widely admired group may be imitated by a much larger population. Some terms also survive because they become attached to a widely consumed cultural product, such as a film or song.

The rise of the internet and mobile phones has transformed the speed at which slang can spread, but it has not abolished the underlying social dynamics. On social media, a new expression can reach millions of users in hours, and platforms allow direct observation of how words are adopted. However, even online, people do not copy everyone equally; they imitate those they admire or identify with. A viral post by a popular creator can launch a term, but ordinary users are more likely to adopt it if their own friends do. Thus the internet is an accelerant, not a replacement for personal networks.

There is a widespread belief that slang is ruining language, but linguists generally reject this view. Slang is neither new nor corrupting; every living language has informal varieties that change over time. What is new is the possibility of tracking those changes in real time. Computational methods now allow researchers to analyse millions of messages and identify which terms are spreading, how quickly, and among whom. This evidence has confirmed that slang follows the same basic patterns as other linguistic changes, but at a faster pace and with more visible intermediate stages. Complaints about the language of young people can be found in writing from ancient times.

One interesting finding from such research is that many expressions are not spread by large numbers of people but by a small group of highly connected individuals. These 'influencers' may not be the original coiners, but they have many social ties and use new words early. By contrast, the majority of speakers are conservative, adopting a term only after they have heard it several times from different sources. The tipping point at which a slang word becomes accepted is difficult to predict, but it often coincides with the moment when the term stops being used as a marker of youth and becomes simply useful. The role of media in amplifying slang is often misunderstood; a word does not become common simply because it appears on television, but because viewers use it with one another.

My own view is that slang is a creative and inevitable part of language change. Attempts to prevent it, whether by teachers or editors, usually fail because they misunderstand its social function. People use slang not to damage the language but to express identity, solidarity and play. At the same time, the rise of global digital media may be making slang less local and more homogeneous, as terms invented in one city are quickly taken up across the world. Whether this reduces linguistic diversity is a serious question, but it does not make slang any less fascinating.