You should spend about 20 minutes on Questions 1-12, which are based on Reading Passage 1 below.
GLOBAL WARMING IN ANTARCTICA
A If you are an aficionado of the global warming "debate", you have probably read at one time or another that current trends in the Antarctic show that there is no such thing as global warming. This is, of course, not true.
B Antarctica can be divided into three major geographic regions: East Antarctica, West Antarctica, and the Antarctic Peninsula. The Transantarctic Mountains divide the continent into eastern (on the Indian Ocean side) and western (on the Pacific Ocean side) regions. The large East Antarctic Ice Sheet flows slowly through most of its interior (10's of meters per year at most), until the ice approaches the coast and is channeled through fast-flowing (100's of meters per year) outlet glaciers. The ice sheet surface is high, dry, and very cold. The West Antarctic Ice Sheet is a faster flowing ice mass that may be vulnerable to rapid changes.
C The Antarctic ice sheets store 90% of the ice on Earth and close to 70% of the planet's fresh water. The West Antarctic ice sheet contains enough ice to raise sea level between 5 and 6 meters, were it all to melt. The East Antarctic Ice Sheet holds about 10 times more. (The total ice volume is larger than this but once the ice is melted, you have to fill in the hole it left behind.) The relatively warm Antarctic Peninsula supports a series of ice caps and outlet glaciers that together are estimated to contain less than half a meter of sea level equivalent. The continent is surrounded, seasonally, by sea ice that freezes at the ocean surface. Just as in the Arctic, sea ice formation in the Antarctic is important to many parts of the Earth system, including ocean circulation and climate.
D The climate of Antarctica does not allow extensive vegetation. A combination of freezing temperatures, poor soil quality, lack of moisture, and lack of sunlight inhibit the flourishing of plants. As a result, plant life is limited to mostly mosses and liverworts. The autotrophic community is made up of mostly protists. The flora of the continent largely consists of lichens, bryophytes, algae, and fungi. Growth generally occurs in the summer and only for a few weeks at most.
E A variety of marine animals exist and rely, directly or indirectly, on the phytoplankton. Antarctic sea life includes penguins, blue whales, orcas, colossal squids and fur seals. The Emperor penguin is the only penguin that breeds during the winter in Antarctica, while the Adelie Penguin breeds further south than any other penguin. The Rockhopper penguin has distinctive feathers around the eyes, giving the appearance of elaborate eyelashes. King penguins, Chinstrap penguins, and Gentoo Penguins also breed in the Antarctic. The Antarctic fur seal was very heavily hunted in the 18th and 19th centuries for its pelt by sealers from the United States and the United Kingdom. The Weddell Seal, a "true seal", is named after Sir James Weddell, commander of British sealing expeditions in the Weddell Sea. Antarctic krill, which congregates in large schools, is the keystone species of the ecosystem of the Southern Ocean, and is an important food organism for whales, seals, leopard seals, fur seals, squid, icefish, penguins, albatrosses and many other birds.
F The passing of the Antarctic Conservation Act in the U.S. brought several restrictions to U.S. activity on Antarctica. The introduction of alien plants or animals can bring a criminal penalty, as can the extraction of any indigenous species. The overfishing of krill led officials to enact regulations on fishing. The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), a treaty that came into force in 1980, requires that regulations managing all Southern Ocean fisheries consider potential effects on the entire Antarctic ecosystem. Despite these new acts, unregulated and illegal fishing, particularly of Patagonian toothfish (marketed as Chilean Sea Bass in the U.S.), remains a serious problem. The illegal fishing of toothfish has been increasing, with estimates of 32,000 tonnes (35,300 short tons) in 2000.
G Most of the continent's icy mass has so far proven largely impervious to climate change, being situated on solid rock; its deep interior is actually growing in volume as a result of increased precipitation. The Antarctic contribution to sea-level rise has long been uncertain. A recent report by CPOM suggests that Antarctica has provided, at most, a negligible component of observed sea-level rise – indeed a survey of 72% of the Antarctic ice suggests an attributable short-term lowering of global sea levels by 0.08 mm per year. Conversely, a 10-year comparison of the balance between glacier decline and snowfall accumulation found that ice loss had increased 75%. In 2006, Antarctica lost a net 200 billion tonnes of ice.
You should spend about 20 minutes on Questions 13-25, which are based on Reading Passage 2 on the following pages.
A BRIEF HISTORY OF RUBBER
A Rubber is one of the most important products to come out of the rainforest. Though indigenous rainforest dwellers of South America have been using rubber for generations, it was not until 1839 that rubber had its first practical application in the industrial world. In that year, Charles Goodyear accidentally dropped rubber and sulfur on a hot stovetop, causing it to char like leather yet remain plastic and elastic. Vulcanization, a refined version of this process, transformed the white sap from the bark of the Hevea tree into an essential product for the industrial age.
B With the invention of the automobile in the late 19th century, the rubber boom began. As demand for rubber soared small dumpy river towns like Manaus, Brazil, were transformed into overnight into bustling centres of commerce. Manaus, situated on the Amazon where it is met by the Rio Negro, became the opulent heart of the rubber trade. Within a few short years Manaus had Brazil's first telephone system, 16 miles of streetcar tracks, and an electric grid for a city of a million, though it had a population of only 40,000. Vast fortunes were made by individuals, and flaunting wealth became sport. Rubber barons lit cigars with $100 bank notes and slaked the thirst of their horses with silver buckets of chilled French champagne. Their wives, disdainful of the muddy waters of the Amazon, sent linens to Portugal to be laundered. They ate food imported from Europe. And in the wake of opulent dinners, some costing as much as $100,000, men retired to any one of a dozen elegant bordellos. The citizens of Manaus were the highest per capita consumers of diamonds in the world.
C The opulence of the rubber barons could only be exceeded by their brutality. Wild Hevea trees, like all primary rainforest trees are widely dispersed, an adaptation that protects species from the South American leaf blight which easily spreads through and decimates plantations. Thus to make a profit, barons had to acquire control over huge tracts of land. Most did so by hiring their own private armies to defend their claims, acquire new land, and capture native labourers. Labour was always a problem so barons got creative. One baron created a stud farm, enslaving 600 Indian women whom he bred like cattle. Other barons like Julio Cesar Arana simply used terror to acquire and hold on to Indian slaves. Indians captured usually submitted because resistance only meant more suffering for the families. Young girls were sold as whores, while young men were bound, blindfolded, and had their genitals blasted off. As the Indians died, production soared: in the 12 years that Arana operated on the Putumayo River in Colombia, the native population fell from over 30,000 to less than 8,000 while he exported over 4,000 tons of rubber earning over $75 million. The only thing that stopped the holocaust was the downfall of the Brazilian rubber market.
D The Brazilian rubber market was crushed by the rapid development of the more efficient rubber plantations of Southeast Asia. However, the prospects of developing plantations did not begin on a high note. Rubber seeds, rich with oil and latex, could not survive the long Atlantic journey from Brazil. Finally, in 1876, an English planter, Henry Wickham, collected 70,000 seeds and shipped them to England. (This shipment remains a source of controversy. Brazilians, conveniently forgetting their entire agricultural economy is based on six imported plants – African oil palm, coffee from Ethiopia, cacao from Colombia and Ecuador, soybeans from China, and sugarcane from Southeast Asia – still speak of the "rubber theft" as a moment of infamy. Wickham himself, in his memoirs, lent a note of mystery to the deed, no doubt intending to elevate his own profile in the eyes of his peers. In fact, all evidence suggests that the exportation was a straight forward affair conducted in the open and actively facilitated by the Brazilian authorities in Belem.) In either case, 2,800 of the seeds germinated and were sent to Colombo, Ceylon (present day Sri Lanka). After several false starts, including one planter in northern Borneo who felled his plantation after finding no rubber balls hanging from the branches, the prospects were grim. One major obstacle was the success of tea (Ceylon) and coffee (Malaya) gave planters no reason to try an untested crop.
E Finally in 1895, Henry Ridley, head of Singapore's botanical garden, persuaded two coffee growers to plant two acres of Hevea trees. Twelve years later more than 300,000 ha of rubber grew in plantations in Ceylon and Malaya. New innovations increased efficiency and production doubled every two years. Rubber could be produced at only a fraction of the cost of collecting wild rubber in Brazil. By 1910, Brazilian production had fallen to 50%. In 1914, Brazil's market share was down around 30%; 1918 – 20%, and 1940 – 1.3%.
F However the Second World War threatened to shift the rubber wealth. With Japan occupying prime rubber producing areas in Southeast Asia, the US feared it would run out of the vital material. Every tire, hose, seal, valve, and inch of wiring required rubber. The Rubber Development Corporation, the chief overseer of rubber acquisition, sought out other sources including establishing a rubber programme that sent intrepid explorers into the Amazon seeking rubber specimen that would be used to produce high yields, superior product, and possibility of resistance against leaf blight. The ultimate goal of the program was to establish rubber plantations close to home. In addition to searching the Amazon and establishing experimental plantations in Latin America, the programme came up with some novel plans to produce rubber including planting Dandelions in 41 states. Extensive work on synthetic rubber yielded a product that, in time, economists predicted would replace natural rubber. By 1964 synthetic rubber made up 75% of the market.
You should spend about 20 minutes on Questions 26-40, which are based on Reading Passage 3 below.
SLEEPING
Sleep medicine is a relatively young field in the UK, with only a couple of centres until the 1980s. In the last decade a number of centres have sprouted, often led by chest physicians and ENT surgeons with an interest in obstructive sleep apnoea, forcing neurologists and neurophysiologists to wake up and contribute to the non-respiratory aspect of this neglected subject.
Within sleep, two states are recognised – non rapid eye movement (NREM) and rapid eye movement (REM). These alternate cyclically through the night with cycle time of 90 minutes (50-60 minutes in the newborn). NREM sleep is divided into four stages: stages 1 and 2 (considered light sleep), and stages 3 and 4 (deep sleep with high arousal threshold).
REM is ontogenically primitive with EEG activity closer to wake state, intermittent bursts of REMs and muscle atonia interrupted by phasic bursts producing asynchronous twitching. The atonia of REM sleep prevents acting out of dreams and is lost in REM behaviour disorder when dreams content becomes violent and patients act out their dream, often resulting in injury. REM behaviour disorder can be a precursor of neurodegenerative disease including Parkinsons. Dream content (pleasant/unpleasant) will be remembered on waking from REM sleep but there is often little memory of the preceding mental activity on arousals from NREM sleep, even when associated with complex behaviours and autonomic disturbance as occurs in night terrors or sleep walking.
In the newborn 50 per cent of total sleep time is occupied by REM sleep, progressively shrinking to 25 per cent in the adult, the first block of REM sleep occurring about 90 minutes after sleep onset. Abrupt withdrawal of alcohol and many centrally acting recreational and non-recreational drugs can cause REM sleep to occur at sleep onset. This can also increase total REM sleep, leading to intense vivid often frightening dreams (hypnogogic-sleep onset/hypnopompic or, on waking, hallucinations), similar to that experienced by patients with narcolepsy.
The NREM/REM sleep states are interrupted by brief arousals and transient awakenings. The frequency of the arousals may increase with emotional disturbance or environmental discomfort but also in many intrinsic sleep disorders such as periodic leg movements in sleep, obstructive sleep apnoea and narcolepsy.
A basic rest-activity cycle originates in fetal life. The newborn sleeps an equal amount during the day and night, the sleep-wake cycle organised around three- to four-hourly feeds. By the second month favouring of sleep towards night-time occurs and by six months the baby will have about 12 hours of sleep at night in addition to a couple of daytime naps. In general, children born prematurely have a tendency to be awake more at night in the first year and breast-fed babies wake more frequently, but the difference disappears by the second year. Persistent night awakenings in infants and toddlers usually reflect the child's inability to self-soothe back to sleep without parental attention and will respond to a well-supported behavioural programme.
The establishment of a consolidated night sleep pattern in children reflects brain maturation and may be disrupted in children with developmental problems. Even in this group success is possible by persisting with behavioural work, though many paediatricians prescribe melatonin for these children with some success. But as the long-term safety of melatonin remains unknown it should be used as a last resort. There are now good studies looking at short-term use of melatonin in sleep-wake cycle disorders such as delayed sleep phase syndrome. Its use as a hypnotic should be discouraged, especially in the developing child as there is uncertainty on other cycles, such as menstrual.
In addition to the NREM/REM cycles, there is a circadian (24 hours) sleep/wake cycle entrained by intrinsic rhythms (melatonin and body temperature) and extrinsic factors (light and social cues such as mealtimes, school/work times). The pineal hormone melatonin plays a role in entraining the sleep-wake cycle to the light-dark cycle. Melatonin secretion is high in darkness and low in daylight hours, the process beginning in the retina with the supra-chiasmatic nucleus playing a major role as a sleep regulator via melatonin. Blind people may lose this entrainment and develop a free running sleep/wake cycle with progressive advancement of sleep onset time.
Polymorphism of the circadian clock gene has now been identified with the population divided between morning types (larks) and evening types (owls). Those predisposed to later sleep onset time (evening types) are susceptible to developing delayed sleep phase syndrome especially during adolescence when sleep requirement increases and there is a tendency towards later time for sleeping and waking. In delayed sleep phase syndrome, sleep onset is delayed to the early hours of the morning with consequent difficulty in waking in time for school/work. Once established, advancing sleep onset time is difficult and requires treatment with appropriately timed melatonin or bright light therapy – advancing sleep onset progressively forwards until the desired sleep time is reached.
In contrast the elderly who are more susceptible to perturbation in their sleep-wake schedule can develop advanced sleep phase syndrome with sleep onset occurring early in the evening. Shift workers often struggle to cope with shift patterns as they grow older due to difficulty in re-adjusting their circadian clock. In general, morning bright light exposure is a more powerful synchroniser of the circadian rhythm than melatonin.