IELTS Academic Reading Practice Test 7

A Why we dream is regarded as one of the oldest unanswered questions in human science. The ancient Egyptians believed dreams were messages from the gods, recorded in dream books that survive from the second millennium BCE. Aristotle, by contrast, argued in his treatise On Dreams that dream content was a product of physical disturbances during sleep, and bore no special significance. The scientific study of dreaming is widely said to have begun in earnest only with the discovery of rapid eye movement sleep in 1953 by Eugene Aserinsky and Nathaniel Kleitman, who showed that volunteers woken from periods of rapid eye movement reported vivid dreams roughly 80 percent of the time, compared with around 7 percent of awakenings from other stages.

B Modern theories of dream function generally tend to fall into one of three broad camps. The first, drawing on a tradition going back to Sigmund Freud, treats dreams as expressions of repressed psychological content. While Freud's specific theories of dream interpretation have largely fallen out of favour in scientific psychology, the broader idea that dreams reflect unresolved emotional concerns has survived in modified form. A second camp treats dreams as essentially a by-product of brain processes that serve other purposes, with no specific function of their own — the so-called activation-synthesis hypothesis, proposed in 1977 by Allan Hobson and Robert McCarley.

C A third and increasingly influential view holds that dreams play an active role in emotional regulation and memory consolidation. Studies by neuroscientist Matthew Walker and others have shown that rapid eye movement sleep reduces the emotional charge of recent memories, suggesting an overnight processing function. Participants in laboratory studies have been shown to perform better on creative problem-solving tasks after a period of sleep containing rapid eye movement than after the same period spent awake, even when total sleep time is controlled. This points to a constructive role in which dreaming may help integrate new experiences with existing knowledge.

D The neurobiology of dreaming has been mapped in increasing detail. During rapid eye movement, the prefrontal cortex — the brain region most associated with executive control and logical reasoning — shows reduced activity, while the limbic system involved in emotion is highly active. This pattern is thought to explain dreams' characteristic combination of intense emotion and weak logical structure: the brain is generating vivid scenarios but is unable to evaluate them critically. Curiously, the regions of the visual cortex that process imagery are also reportedly strongly activated, despite the eyes being closed and the sensory input absent.

E Sleep paralysis during dreaming is mediated by the brainstem, which actively inhibits voluntary muscle activity through neurotransmitters including glycine and gamma-aminobutyric acid. This inhibition prevents the dreamer from physically enacting their dreams. Disorders of this inhibitory system can produce dramatic clinical syndromes. In rapid eye movement sleep behaviour disorder, the inhibition fails and sufferers physically act out their dreams, sometimes with violent consequences. The disorder, more common in older men, has been linked to elevated long-term risk of Parkinson's disease and other neurodegenerative conditions.

F Lucid dreaming — described as the experience of being aware that one is dreaming while still asleep — has attracted growing scientific attention. Experiments in which lucid dreamers communicate with researchers through pre-arranged eye movements have shown that conscious problem-solving can occur during dreams, and several training techniques have been shown to increase the frequency of lucid dreams in motivated subjects. Therapists have begun to use such techniques as treatment for chronic nightmares, with what many describe as promising preliminary results.

G The cross-cultural study of dreams reveals both striking universals and significant variation. Themes of falling, being chased, and appearing inappropriately in public are reported almost everywhere, but the meanings attributed to dreams differ profoundly. Many traditional societies generally treat dreams as a source of practical guidance or contact with ancestors. The growing tendency in industrialised societies to dismiss dreams as random neural noise may itself, in the writer's view, be a recent and culturally specific perspective, rather than a universal scientific finding.

A The world's wild fisheries reportedly supply roughly one-fifth of the animal protein consumed by humans and directly employ around 60 million people, the great majority of them in small-scale operations in developing countries. The total annual catch from wild marine fisheries has been roughly stable at between 80 and 90 million tonnes since the early 1990s, despite continued growth in fishing effort. The plateau, in many marine biologists' view, is not a coincidence but a sign that the limits of natural productivity have been reached, and in many regions exceeded, by a global fleet that has grown both in size and in technical sophistication.

B A simple economic intuition explains how this happens. Fish in the open ocean are a common-pool resource: nobody owns them until they are caught, and any catch by one operator reduces the stock available to others. In the absence of effective regulation, individual operators have, on the whole, no incentive to leave fish in the water for the future, since whatever they choose not to catch may simply be taken by competitors. The economist H. Scott Gordon described this dynamic in a 1954 paper that is widely regarded as foundational to fisheries economics, showing that an open-access fishery would expand until rents were dissipated and the stock was reduced well below its maximum productive level.

C Modern fisheries management has developed a range of regulatory tools to address these incentive problems. The most basic is the establishment of a total allowable catch, set each season by scientific committees on the basis of stock assessments. Limited entry licensing restricts the number of vessels permitted to participate. Seasonal closures and gear restrictions reportedly reduce by-catch and protect spawning grounds. None of these tools, however, generally fully resolves the underlying race to fish: each operator still typically has an incentive to catch as much as possible before the seasonal quota is exhausted.

D The most economically influential modern reform is widely said to have been the introduction of individual transferable quotas. Under this system, each operator is allocated a share of the total allowable catch, which they can either harvest themselves or sell to other operators. Because the quota represents an asset whose value depends on the long-term health of the stock, holders reportedly develop a financial interest in conservation. New Zealand introduced the first comprehensive system in 1986, and Iceland, Norway, and parts of the United States have adopted similar regimes. Studies have found improved economic outcomes and stock health under transferable-quota systems, although concerns about concentration of ownership and the marginalisation of small-scale operators have, on the whole, prompted continuing debate.

E The role of subsidies in fisheries economics has attracted growing scrutiny. Global fisheries subsidies are estimated at roughly $35 billion annually, of which perhaps $22 billion subsidises fuel, vessel construction, and other forms of fishing capacity expansion. Critics argue these capacity-enhancing subsidies generally contribute directly to overfishing by sustaining a fleet that the underlying biology cannot support. The World Trade Organization concluded a long-negotiated agreement in 2022 prohibiting subsidies that support illegal, unreported, and unregulated fishing, although implementation has, in many observers' view, been gradual and exempt categories remain.

F Marine protected areas have grown in extent and ambition. The 2010 Aichi Biodiversity Targets called for 10 percent of coastal and marine areas to be protected by 2020, a goal that was reached. The Kunming-Montreal framework adopted in 2022 raised the target to 30 percent by 2030. Well-designed protected areas have been shown to allow rebuilding of fish populations within their boundaries, with spillover benefits to adjacent fishing grounds. The effectiveness of any individual reserve, however, depends heavily on enforcement, which remains weak in many remote ocean regions.

G Aquaculture has grown faster than wild capture over recent decades and now supplies roughly half of all fish for human consumption. Salmon, shrimp, and bivalves typically dominate the export-oriented aquaculture industry, while freshwater carps and tilapias supply most aquaculture protein consumed within producing countries. Environmental concerns generally include water pollution, escape of farmed fish into wild populations, and reliance on wild fishmeal to feed carnivorous species. New approaches including land-based recirculating systems and improved feed formulations are addressing some of these challenges, although at higher cost.

A A glacier is, in essence, described as a river of ice. The accumulation of snow at high elevations, year after year, eventually compresses lower layers into dense ice that flows slowly downhill under its own weight. Although the speeds involved are measured in metres per year, the cumulative effect of glacier movement is widely said to have carved spectacular landscapes — the U-shaped valleys, fjords, and moraines that define much of the polar and high-mountain world. Understanding how glaciers move, and how that motion is changing, has, in many earth scientists' view, become one of the central problems of modern earth science.

B Two principal mechanisms generally drive glacier flow. Internal deformation occurs as the ice itself slowly deforms under pressure, with grains rearranging and individual crystals deforming along planes of weakness. Basal sliding occurs at the bottom of the glacier, where a thin film of meltwater allows the entire ice mass to slip over the underlying rock. The balance between the two mechanisms varies enormously between glaciers. Cold polar glaciers, generally frozen solidly to their beds, reportedly move almost entirely by internal deformation. Temperate glaciers, with significant basal meltwater, can be dominated by basal sliding, which produces much faster flow rates.

C Glaciologists generally divide a glacier into two functional regions. The accumulation zone is where snowfall exceeds melting and the ice mass grows. The ablation zone is where melting and other losses exceed accumulation, and the ice mass shrinks. The boundary between them is called the equilibrium line. The position of the equilibrium line shifts with climate: a warming atmosphere pushes it to higher altitudes, expanding the ablation zone and shrinking the glacier overall. Mass balance — the net annual gain or loss of ice — is measured at thousands of glaciers worldwide and has been overwhelmingly negative for several decades.

D The acceleration of glacier loss since the 1980s is, on the whole, well documented. The World Glacier Monitoring Service estimates that mountain glaciers globally lost an average of around 0.5 metres of water-equivalent ice per year over the 1990s, rising to over one metre per year by the 2010s. Specific iconic glaciers have lost dramatic proportions of their ice: Bolivia's Chacaltaya glacier disappeared entirely in 2009, and the Tibetan Plateau's largest glaciers are projected to lose two-thirds of their mass by 2100 under intermediate warming scenarios. Beyond the obvious aesthetic loss, glacier retreat reportedly has direct hydrological consequences: many major rivers, including the Ganges, Indus, and Mekong, are partly fed by glacial meltwater, and the timing of their flow is being altered.

E Antarctic and Greenland ice sheets are vastly larger than mountain glaciers and contain enough ice to raise global sea levels by approximately 65 metres if entirely melted. Although total melting is geologically slow, the dynamic response of these ice sheets to warming is widely said to have been faster than earlier projections suggested. Marine-terminating glaciers in West Antarctica have been observed accelerating and thinning as warm ocean water erodes their floating ice shelves, removing the buttressing effect that had held the upstream ice in place. Some researchers argue that parts of the West Antarctic Ice Sheet may already be committed to irreversible decline regardless of future emissions, although the issue, in many analysts' view, remains actively debated.

F Beyond their direct contribution to sea level, glaciers generally play a complex role in regional climate. The high albedo of fresh snow and ice reflects up to 90 percent of incoming solar radiation, while exposed rock and ocean generally absorb most of it. As glaciers retreat and expose darker surfaces, additional solar energy is absorbed, accelerating further warming — a positive feedback known as the ice-albedo effect. The deposition of light-absorbing particles such as black carbon from combustion and biological pigments produced by snow algae reportedly further darkens snow surfaces and reinforces the effect.

G Modelling future glacier evolution remains scientifically challenging. The processes involved typically range from microscopic crystal mechanics to ocean-circulation patterns spanning thousands of kilometres, and the equations describing them are not all closed-form. Recent advances in remote sensing — particularly satellite radar and laser altimetry — have transformed the observational picture, providing precise repeat measurements of ice elevation across the entire planet. Whether modelling can keep pace with rapidly changing real-world ice behaviour will, in many writers' view, largely determine how well societies can plan for the consequences of a deglaciating world.