IETLS Academic Reading Test 1

Bats are the only mammals capable of sustained, powered flight, and the majority of the more than 1,400 known species are also capable of navigating and hunting in complete darkness using a biological sonar system known as echolocation. Because their eyes are often poorly adapted for detailed vision at night, bats instead build a detailed acoustic picture of their surroundings by emitting rapid pulses of high-frequency sound and interpreting the returning echoes. Unlike some other forms of animal signalling, biosonar calls are produced by both male and female bats in more or less equal measure, and the calls themselves vary considerably depending on the species, the surrounding habitat and the task at hand.

The systematic study of this remarkable ability is generally credited to the bioacoustics researcher Dr Anton Reyes, who in the early 1980s constructed a series of soundproofed flight chambers fitted with ultrasonic microphones in order to record bats in mid-pursuit of live insects. Reyes and his team released moths into the chambers and used high-speed cameras alongside the recording equipment to correlate each bat's changing call pattern with its position relative to the target. What his research revealed was that the acoustic pattern of a bat's call changes in a highly predictable way as it draws closer to its prey, and that both the distance and the direction of an object can be estimated from acoustic cues alone.

A hunting bat typically produces three distinct types of call, depending on how far away the target is. When searching a wide area for potential prey, the bat emits what is known as a search-phase call: a relatively long pulse separated from the next by a comparatively wide gap, often several hundred milliseconds. Once a target has been detected and the bat begins closing in, it switches to an approach-phase call, shortening both the length of the pulse and the gap between pulses so that it receives more frequent updates on the target's position. In the final moments before contact, the bat produces what researchers call a terminal buzz, in which pulses are emitted in extremely rapid succession, with the interval between them shortening to as little as five milliseconds. This burst of information allows the bat to track even the sudden evasive movements of an insect attempting to escape.

Determining the direction of a target requires a different mechanism altogether. Because a bat's two ears are positioned slightly apart and often shaped asymmetrically, an echo bouncing off an object to one side of the bat will arrive at the nearer ear a fraction of a second earlier, and at a marginally higher intensity, than it does at the farther ear. The bat's auditory system is exquisitely sensitive to these minute differences in arrival time and loudness, and by comparing the two signals it can calculate the angle of the target relative to its own flight path with an accuracy of only a few degrees. Because the bat is also moving during this process, it continuously updates this angular estimate with each successive call, effectively producing a constantly refreshed map of everything around it.

Not every researcher, however, accepts that echolocation alone accounts for the hunting success of bats. Dr Marta Ilves and her colleagues have argued that vision may play a supplementary role, particularly during twilight hours when ambient light levels are still relatively high. In one experiment, Ilves fitted a group of bats with lightweight blindfolds and compared their hunting success in dim light with that of an unblindfolded control group. The blindfolded bats were still able to capture prey, but did so less efficiently, taking noticeably longer to intercept moving targets. Ilves concluded that echolocation is clearly sufficient on its own to allow a bat to hunt successfully, but that residual vision appears to offer a modest additional advantage when available, helping the animal react a little more quickly to a target's movements.

AParagraph A Recent research conducted in Singapore indicates that fitting residential tower blocks with vegetated 'green' roofs can meaningfully reduce indoor temperatures during the hottest months of the year, easing dependence on mechanical air conditioning. The study, which examined buildings constructed between 1990 and 2015, found that flats situated directly beneath a green roof recorded significantly lower peak temperatures than equivalent flats in buildings with conventional concrete roofing. Published in the journal Urban Ecology, the findings add to a growing body of research linking vegetated rooftops to lower energy consumption in dense cities.

B Paragraph B The research team, led by Dr Priya Nair of the National University of Singapore, believes that the cooling effect stems from two combined mechanisms. First, the layer of soil and vegetation physically shades the roof surface from direct sunlight, preventing heat from being absorbed into the building's structure. Second, the plants continuously lose water vapour through a process called evapotranspiration, which draws heat away from the surrounding air in much the same way that sweating cools the human body. Engineers had long suspected that shading alone was responsible for the effect, but Nair's team believes this is the first study to properly quantify the additional contribution made by evapotranspiration.

C Paragraph C Since the 1990s, the so-called urban heat island effect, in which densely built cities trap significantly more heat than surrounding rural areas, has been intensifying across South East Asia, and architects and urban planners fear that rising cooling costs could place a growing strain on electricity grids. Although some earlier estimates have since been revised downward, current projections suggest that by 2030 close to one in three residential buildings in Singapore's city centre will require some form of supplementary cooling infrastructure beyond standard air conditioning. Ten years ago, forecasts for the same period were considerably higher, predicting that nearly half of all buildings would need such measures.

D Paragraph D The relationship between rooftop vegetation and indoor temperature has attracted growing attention over the past decade, with earlier studies showing that a poorly insulated roof can be responsible for a substantial share of a building's total heat gain during summer months. Nair and her colleagues set out to establish whether green roofs could meaningfully offset this problem in a tropical climate. They surveyed just over 3,000 residential units across 40 buildings, collecting data on roof type, indoor temperature, air conditioning use and residents' reported comfort levels. On an average afternoon in the dry season, uninsulated concrete roofs allowed indoor temperatures to climb more than six degrees above the outdoor shade temperature.

E Paragraph E What the researchers found most striking was that buildings fitted with a well-maintained green roof recorded indoor temperatures that were, on average, four degrees lower during peak afternoon hours than those in buildings with a bare concrete roof, and that residents in these buildings reported switching on their air conditioning noticeably less often. A summary of the findings noted: "Buildings with a neglected or sparsely planted green roof showed only a marginal cooling benefit compared with a healthy, densely planted one. Our data suggest that the condition of the vegetation, not merely its presence, is what determines the scale of the cooling effect."

F Paragraph F The study authors observed that a substantial minority of the green roofs surveyed had been allowed to fall into disrepair, with patches of dead or dying vegetation exposing bare soil or roofing membrane to direct sunlight. However, the researchers were not entirely sure why some building managers neglected their green roofs while others invested heavily in their upkeep, though they noted that buildings with a dedicated maintenance budget and resident gardening committees tended to have the healthiest rooftop gardens. The team cautioned that a poorly maintained green roof can, in rare cases, even trap moisture against a building's structure, creating a separate risk of water damage if drainage is not properly managed.

G Paragraph G The precise scale of the energy savings that can be achieved through green roofs remains difficult to pin down, according to Professor Daniel Cho, an expert in sustainable architecture at a Hong Kong-based research institute who was not involved in the Singapore study. "There are clearly measurable reductions in surface and indoor temperature," Cho said, "but a building's orientation, the thickness of its walls and even the colour of its exterior paint all interact with a green roof in ways that are still not fully understood." In the meantime, Cho advises building managers considering a green roof to prioritise a realistic long-term maintenance plan over simply maximising the area of vegetation installed, since an unmaintained roof garden may ultimately deliver little benefit at a considerable ongoing cost.

Particularly as organisations increasingly rely on distributed teams working from different cities, or even different countries, maintaining consistent productivity without the informal oversight of a shared office has become a significant management challenge. While some companies have responded by cutting back on structured communication in the hope of maximising employee autonomy, a growing number are investing heavily in frameworks specifically designed to keep remote teams aligned and motivated.

Priya Chandran of Meridian Workplace Consulting argues that one of the most persistent obstacles she encounters is that senior leaders often recognise that 'team cohesion' matters for remote staff but are unable to articulate precisely what that means in practice. In a traditional office, she says, cohesion is visible in small daily interactions; in a distributed team, it must be deliberately engineered rather than left to develop naturally. Chandran maintains that it is more useful to define a remote team not simply as a group of people who share a manager, but as a group working towards a clearly articulated common outcome, whether that is a shared sales target, a joint product launch or the broader success of the organisation as a whole.

Marcus Webb of Distant Peak Advisory believes that some degree of friction is inevitable in any team whose members rarely meet face to face, since misread tone in written messages and differing time zones will unavoidably lead to occasional misunderstandings. A resilient distributed team, he argues, can nonetheless be built in any organisation prepared to invest deliberately in its remote culture. While hiring external consultants to design remote-working programmes can be expensive, Webb notes that companies with an established internal HR function are increasingly designing these programmes themselves. Northline Collective, founded in 2015 and led by Sofia Bianchi, offers free guidance to companies wishing to design their own onboarding and engagement programmes in house, in the belief that tailored, company-specific training is always more effective than generic material. Northline's own revenue model relies on advertising carried on its widely read online resource hub, which has comfortably exceeded its projected readership figures in every year since launch.

Bianchi compares effective distributed teamwork to the trust built between members of a small expedition crew, arguing that the same bonds of empathy and mutual reliance developed on a shared physical journey can also be cultivated among colleagues who have never met in person. She holds that strong remote teamwork depends on visible recognition of effort, consistent encouragement and a workplace culture that actively checks in on wellbeing rather than only on output. Attempts to closely monitor or micromanage remote staff, Bianchi warns, tend to erode the very trust they are meant to protect.

Derek Holt, Head of People at Calder Logistics, believes that engagement programmes designed internally tend to outperform externally purchased alternatives for two main reasons. Most importantly, he says, employees are considerably easier to motivate when they can help shape the initiatives themselves, a level of consultation that is far easier to achieve through an internal team than through an outside provider. Almost as important, Holt argues, is that any activity must be perceived by participants as genuinely building their own skills rather than existing simply to fill a calendar slot; programmes designed by people who already understand a company's particular culture are more easily tailored to its distinctive needs.

According to Holt, one of the most common barriers to successful remote engagement programmes is a perception among staff that virtual social activities are contrived or unnecessary, causing many employees to dismiss their hidden value in sustaining long-term collaboration. Chandran, however, maintains that when properly designed and combined with more conventional communication tools, such activities can be a considerable asset. She frames the overall process as four sequential stages, beginning with the first stage: establishing shared expectations across the whole team. This is followed by identifying the specific barriers preventing the team from meeting those expectations, before introducing appropriate enablers, such as structured weekly check-ins, to address them directly. The fourth and final stage involves measuring outcomes against the original expectations, with progress then continuously monitored to ensure gains are sustained over time. Chandran believes that in the second and third stages in particular, informal, lightly humorous communication helps to build the kind of personal rapport that formal processes alone rarely achieve.

Naomi Frost, People Director at Ashford Textiles, agrees that combining structured process with informal rapport-building can substantially improve outcomes for distributed teams. She has recently designed a ten-week remote-engagement programme for the company's senior leadership group and is preparing to deliver the first of six planned workshops. The stated goal of the project is to strengthen collaboration across five departments spread over three countries, involving roughly 150 staff members in total. The programme is explicitly experimental, Frost says, and if successful will be extended to the company's other regional offices. Previously, the organisation had relied on more conventional approaches such as quarterly surveys and formal performance reviews. The new approach is considerably more informal by comparison, including one exercise in which each department must produce a short recorded video introducing its work to colleagues in other countries.

Approaches to sustaining productivity and cohesion in distributed teams vary enormously in method, theory and underlying philosophy, and specialists broadly agree that no single approach succeeds in every organisational culture. A close fit between the chosen method and the personalities involved appears to be critical to its success, and thoughtful, consistent follow-up is just as important as the initial programme itself.