IELTS Academic Reading Practice Test 11

Before the 1940s, a scratch that became infected could kill. Doctors had few effective weapons against bacterial infections: wounds were cleaned and drained, and many patients with pneumonia or blood poisoning simply died. Even minor surgery carried a serious risk of infection, and fevers following childbirth killed large numbers of women. The discovery of penicillin, the first antibiotic to be used widely, changed this. The story of how it happened, however, is less simple than the popular version, in which a single scientist makes a lucky observation and medicine is transformed overnight.

That observation was made by Alexander Fleming, a bacteriologist at St Mary's Hospital in London. Returning from a summer holiday in September 1928, he examined a set of culture plates on which he had been growing Staphylococcus bacteria, and noticed that one had been contaminated by a mould. Around the mould, the colonies of bacteria had been destroyed. Fleming identified the mould as a species of Penicillium and named the substance it released penicillin. He published his findings in 1929, showing that the substance could kill many kinds of disease-causing bacteria without harming white blood cells.

Fleming was not the first person to notice that moulds could inhibit bacteria; several nineteenth-century scientists had reported similar effects. Nor did he develop penicillin into a medicine. The substance proved unstable and difficult to purify in useful quantities, and although Fleming suggested that it might have medical uses, he devoted relatively little effort to pursuing them. In his own laboratory it served mainly as a practical tool for separating certain bacteria from others in mixed cultures. During the 1930s, interest in antibacterial drugs focused instead on the synthetic sulphonamides, the first of which was introduced in Germany in the middle of the decade. For about ten years, penicillin remained little more than a scientific curiosity.

The decisive work was done at the University of Oxford, where in 1939 the pathologist Howard Florey and the biochemist Ernst Chain began a systematic study of natural antibacterial substances. Producing enough penicillin even for experiments was a formidable problem. The mould was grown on the surface of a nutrient liquid, and because of wartime shortages the team improvised, using baths, milk churns and, eventually, specially made ceramic vessels modelled on bedpans. A group of young women recruited to tend the cultures became known as the penicillin girls. Another member of the team, Norman Heatley, devised an ingenious method of extracting the drug, transferring it from the liquid into a solvent and back into water by altering the acidity, and he built much of the apparatus himself.

On 25 May 1940 the team carried out a crucial experiment. Eight mice were injected with a lethal dose of streptococcal bacteria, and four of them were then given penicillin. By the following morning the four untreated mice were dead, while those that had received the drug survived. The results were published in The Lancet in August 1940. The first human patient, a police constable named Albert Alexander, was treated in February 1941 for a severe infection. He improved dramatically, but supplies were so limited that penicillin was recovered from his urine so that it could be used again. When it finally ran out, the infection returned and he died.

It was clear that production on an industrial scale was needed, and wartime Britain lacked the resources. In 1941 Florey and Heatley travelled to the United States, where they worked with government scientists at the Northern Regional Research Laboratory in Peoria, Illinois. There, researchers discovered that adding corn steep liquor, a by-product of the maize industry, to the growth medium greatly increased the yield.

They also developed methods of growing the mould in large tanks rather than in shallow vessels. A search for more productive strains led to a mouldy cantaloupe melon bought at a market in Peoria, which carried a strain far more productive than Fleming's original. American pharmaceutical companies then expanded production rapidly, and by the time of the Normandy landings in June 1944 large quantities were available to treat Allied soldiers.

In 1945 Fleming, Florey and Chain shared the Nobel Prize in Physiology or Medicine. Heatley, whose technical skill had been essential, received no share, although his contribution was later widely acknowledged. Fleming became by far the most famous of the group, partly because newspapers found the tale of an accidental discovery more appealing than the Oxford team's painstaking work. In the same year the chemist Dorothy Hodgkin determined the molecular structure of penicillin using X-ray crystallography, work that helped chemists to create new, modified forms of the drug. Penicillin works by interfering with the construction of bacterial cell walls, so that the bacteria burst. Human cells, which lack such walls, are unaffected.

Fleming himself anticipated the problem that now threatens this achievement. In his Nobel lecture he warned that bacteria exposed to doses of penicillin too small to kill them could become resistant to the drug. Within a few years of its widespread use, resistant strains of Staphylococcus were spreading in hospitals, and resistance to antibiotics has since become one of the most serious challenges facing modern medicine.

Along the rocky coasts of the North Pacific, underwater forests of kelp – large brown seaweeds that can grow more than 30 metres tall – provide food and shelter for a remarkable diversity of fish, invertebrates and marine mammals. Kelp has no roots. Each plant is anchored to the rocks by a structure called a holdfast, and gas-filled bladders keep its long fronds close to the sunlit surface, where they form a dense canopy. Giant kelp is among the fastest-growing organisms on Earth, capable in favourable conditions of lengthening by more than half a metre in a single day. Kelp forests grow in cool, nutrient-rich coastal waters in many parts of the world, but those of the North Pacific are among the most extensive. Yet the health of these forests depends to a surprising extent on a single predator: the sea otter.

Sea otters are among the smallest marine mammals, and unlike seals or whales they have no insulating layer of blubber. Instead, they rely on the densest fur of any animal, with up to about a million hairs per square inch, which traps a layer of air against the skin. Keeping warm in cold water also demands an exceptionally high metabolic rate, and an adult otter must eat roughly a quarter of its body weight every day. Otters spend a large part of each day grooming, because fur that becomes matted or soiled quickly loses its ability to insulate; this is why thousands of otters died after the Exxon Valdez oil spill in Alaska in 1989. Their diet consists largely of invertebrates such as sea urchins, crabs, clams and abalone. It is also one of the few mammals known to use tools, often cracking open hard shells with a stone while floating on its back.

That luxurious fur almost led to the species' extinction. After Russian explorers reached the Aleutian Islands in the 1740s, hunters pursued sea otters along the Pacific coast from Japan to Mexico, and their pelts became some of the most valuable furs in the world. By the early twentieth century, a population once numbering in the hundreds of thousands had been reduced to perhaps a couple of thousand animals in scattered, isolated groups. Commercial hunting ended under an international treaty signed in 1911, and the surviving colonies slowly began to recover. Recovery has been uneven, however. The southern sea otter of California, for example, still numbers only around 3,000 animals and is listed as a threatened species.

The recovery gave scientists an opportunity to observe what otters do to their environment. In the early 1970s the ecologists James Estes and John Palmisano compared islands in the Aleutian chain where otters had returned with islands where they were still absent. Around islands with otters, kelp forests flourished. Where otters were missing, sea urchins had multiplied unchecked and grazed the kelp down to bare rock, creating what are known as urchin barrens. The otters, by eating urchins, were indirectly protecting the kelp. Their 1974 paper became a classic illustration of two ideas. The first was the keystone species, a term introduced a few years earlier by the ecologist Robert Paine for a species whose influence on an ecosystem is far greater than its abundance would suggest. The second was the trophic cascade, in which the effects of a predator ripple down through several levels of a food web.

The Aleutian story took an unexpected turn in the 1990s, when otter numbers in the region collapsed. Estes and his colleagues proposed that killer whales, whose usual prey of seals and sea lions had declined, had begun hunting otters instead. As the otters disappeared, urchins returned and the kelp forests shrank once more. The explanation is still debated, but the episode showed how changes in one part of an ocean ecosystem can have far-reaching consequences elsewhere.

Research in other habitats has revealed further benefits. In Elkhorn Slough, an estuary in California, otters feed heavily on crabs. Fewer crabs means more of the small invertebrates that graze algae off seagrass leaves, so the seagrass beds, which serve as nurseries for fish, have become healthier as otters have returned. Healthy kelp forests also absorb carbon dioxide as they grow, and some researchers have argued that protecting otters could therefore make a modest contribution to slowing climate change, although it is uncertain how much of that carbon is stored over the long term.

Today sea otters have returned to much of their former range, helped in part by programmes in the 1960s and 1970s that moved animals from Alaska to coasts where they had been wiped out, such as those of British Columbia and Washington State. Their recovery is not universally welcomed. Otters compete directly with people for shellfish, and fishers who harvest urchins, crabs and abalone have seen catches decline where otters have returned. In northern California, meanwhile, where otters remain absent, the loss of a sea star that also preyed on urchins, combined with a marine heatwave, contributed to the destruction of more than 90 per cent of the bull kelp forests along part of the coast after 2014. Some scientists argue that bringing otters back to these waters could help the forests recover.

In the spring of 2020, office buildings around the world emptied almost overnight. Before the pandemic, according to surveys by the economists Jose Maria Barrero, Nicholas Bloom and Steven Davis, only around 5 per cent of full paid working days in the United States were worked from home. Within weeks the figure had risen to more than half. It has since fallen back, but not to where it was: in recent years roughly a quarter of paid working days in the United States have been worked from home, a level that appears to have stabilised. Remote work, mostly in a hybrid form that combines days at home with days in the office, has become a lasting feature of professional employment.

This shift prompted dramatic forecasts. If people no longer needed to travel to an office, some commentators argued, they would no longer need to live in expensive cities, and the urban centres that had grown so rapidly in previous decades would decline. Such predictions have a long history. Similar claims were made when the telephone spread, and again in the 1990s, when the internet was expected to make physical distance irrelevant. On each occasion, cities not only survived but grew. I see no reason to expect a different outcome this time, although I do expect the city of the future to look somewhat different.

Part of the reason that remote work has persisted is that its effects on productivity are, on balance, less negative than many managers feared. In an influential experiment published in 2015, Bloom and his colleagues studied call-centre employees at Ctrip, a large Chinese travel company, who were randomly assigned to work either from home or in the office.

Those working from home were about 13 per cent more productive, largely because they took fewer breaks and sick days and worked in quieter conditions, and they were less likely to quit. A later study at the same company, published in 2024, found that allowing graduate employees to work from home two days a week reduced resignations by a third without any measurable effect on their performance or promotion prospects.

Yet such studies measure individual performance, often on fairly well-defined tasks, and they may not capture the less visible benefits of working near colleagues. When Microsoft moved its workforce to remote work in 2020, an analysis of communication among more than 60,000 of its employees found that their collaboration networks became more isolated, with fewer connections between different groups. Other research suggests that the costs fall particularly on junior staff. A study of software engineers at a large American company found that those who sat close to their teammates received considerably more feedback on their work than those whose colleagues were located elsewhere, an advantage that is especially valuable early in a career.

None of this would have surprised Alfred Marshall, the British economist who in 1890 described how ideas circulate among people working in the same industry and the same place, so that specialised knowledge becomes common property, absorbed almost without effort. Economists call such benefits agglomeration effects, and they help to explain why productivity and wages tend to be higher in large cities. Remote work does not eliminate these effects, but it may weaken them, especially for the kind of informal learning that happens when people overhear conversations or ask a colleague a quick question.

Where the effects of remote work are most visible is not in the decline of cities as a whole but in the changing geography within them. Bloom and the economist Arjun Ramani identified what they called a donut effect: during the pandemic, residents, businesses and spending moved from the centres of large American cities towards their suburbs, while the cities' overall populations changed far less. Downtown districts built around the five-day office commute have suffered most. Office vacancy rates in the United States have risen to record levels, shops and restaurants that depended on office workers have closed, and public transport systems have lost fare revenue, which in turn threatens the services on which those who still commute depend.

The solution, I believe, lies in making city centres less dependent on offices. Districts that combine workplaces with housing, culture and leisure have generally recovered more quickly than those devoted almost entirely to commerce. Converting surplus offices into homes is one option, though it is often more difficult than it sounds: many modern office buildings are so deep that their interiors are far from any window, and the plumbing required for apartments is costly to install. Some smaller cities, meanwhile, have tried to attract remote workers directly. The programme Tulsa Remote, launched in 2018, offers people who move to Tulsa, Oklahoma, a payment of $10,000.

Remote work, then, is neither the death of the city nor a passing disruption. It has given many workers greater flexibility, which they value highly, and it has exposed how narrowly some urban centres had come to depend on a single activity. Cities have reinvented themselves many times before, for example after the decline of the manufacturing and port industries that once sustained them. The task now is to ensure that they remain places where people want to be, not merely places where they are obliged to go.