IELTS Academic Reading Practice Test 87

A botanical garden is a living collection of plants. The plants are grown for study, teaching, protection and public enjoyment. These gardens are like living museums because each plant is recorded and labelled and used for research. The first such gardens began in Europe in the 1500s, when medical schools needed a ready supply of plants for teaching. Since then they have spread around the world and now help to save plant life that is under threat.

The oldest one still open is in Padua, in northern Italy. It was set up in 1545 for the study of medicinal plants. It has stayed in the same site for hundreds of years, which is why it is so well known. In the past, medical students used it to learn how to recognise plants that could be used in treatments. Britain's oldest garden, the Oxford Botanic Garden, came later in 1621 and had a similar role. These early gardens were closely tied to medical training, and their formal beds helped students locate particular species.

In the 1700s and 1800s, these gardens grew much larger. European states sent plant hunters to distant places to bring back new kinds, such as garden flowers, spices and food crops. The new plants went to gardens in cities such as Amsterdam, Paris and London. These collections aided the growth of classification and also provided material for economic botany, the study of plants that are useful to people. Many common garden and crop plants spread around the world in this way. But this movement was part of colonial systems and often harmed local communities.

Modern gardens carry out several kinds of scientific work. They keep herbaria, which are collections of pressed plant samples used for study, and they record details about the origin, habitat and genetic identity of each living plant. This documentation is essential for accurate identification and for research comparing one plant with another. When a new species is named, a garden can publish a description and share plant material with other institutions. Without such records, much of the knowledge held in living collections would have little value. Accurate records are also needed when plant material is exchanged between gardens. Computer databases now allow gardens to share these records across national borders.

Conservation is now one of the most urgent tasks. Some species can be protected in their natural habitats, an approach known as in situ conservation. Many others, however, survive only in collections away from home. This second strategy is called ex situ conservation, and it includes living plants in gardens and seeds in seed banks. Seed banks keep seeds cold and dry so they can still grow after many years. If a species disappears from the wild, stored seeds may one day be used to bring it back. Seed banks are especially important for plants that cannot be kept easily as living specimens. They provide a back-up if a disease or extreme weather harms a wild population.

The sharing of seeds between gardens is old and well organised. Many gardens publish an Index Seminum, a list of seeds or other plant material that they are willing to give to other gardens. Scientists then ask for items from this list for research or for saving plants. This system has helped spread rare species around the globe.

Gardens are also showing more interest in wild relatives of crops. These wild relatives carry genetic traits that may be needed in later plant breeding, such as resistance to disease, drought and changing conditions. As farm varieties become more alike, these wild relatives are a vital source of resilience to pests and weather. Some crop wild relatives are already kept in specialist collections.

Alongside this research, the gardens now have a strong teaching role. They provide labels, guided tours, courses and citizen science projects, and every year millions of schoolchildren and adults visit them. This role is not only about recreation. By displaying rare plants, gardens hope to build public support for conservation and to show how human welfare depends on plant life. Many gardens also train growers and botanists, especially in countries that contain rich plant life but few training facilities. Public education can change how people treat plants and natural areas. In this way, a visit to a garden may support wider conservation goals.

Botanical gardens face several major problems. Climate change is already altering the conditions in which outdoor plants can grow. Hotter or drier weather can put stress on mature trees and old plantings. Pests and diseases can also arrive through trade and harm both collections and wild areas. Urban growth and pollution reduce the space available for gardens to expand. In response, many institutions work together through regional and global networks, sharing data and plant material so that no single garden has to hold every species alone. Networks also help gardens cope with threats to their own plants. By cooperating, they can share the cost and technical work of maintaining many species.

Despite these pressures, botanical gardens remain irreplaceable. They bring together long-term records, living plants, seeds and specialist knowledge in a way that no other institution can match. In a time of rapid environmental change, their collections are not fixed displays but active resources for research, repair and education. The living library of a botanical garden, planted for the benefit of one generation, may hold the key to food or to a restored landscape for the next. For this reason, support for these gardens should be seen as part of wider efforts to protect the natural world.

Sleep is not a single uniform state, and its appearance varies strikingly across the animal kingdom. Scientists usually identify sleep by a combination of features, including reduced responsiveness, a characteristic posture and a rapid return to wakefulness when stimulated. This behavioural definition allows researchers to study rest in animals as different as a fruit fly and a whale. Although almost every animal studied so far shows some form of rest, the duration, depth and organisation of that rest can differ enormously, and the evolutionary reasons for this variation are still being explored. Comparing rest patterns across species may therefore reveal what sleep is ultimately for.

In mammals and birds, sleep is divided into two broad stages: slow-wave sleep and rapid eye movement, or REM, sleep. During slow-wave sleep the brain produces large, slow electrical rhythms and the body is largely still. During REM sleep the brain becomes highly active, the eyes move rapidly and the muscles are usually paralysed. The functions of these stages remain debated, but researchers have linked slow-wave sleep to physical restoration and REM sleep to learning and memory. Neither stage, however, is necessarily present in the same way in all species. For example, the proportion of time spent in REM sleep can range from very little to several hours, and its exact form may be hard to compare across distant groups.

The most striking example of localised sleep occurs in dolphins and some whales. These animals engage in what is known as unihemispheric slow-wave sleep, in which one hemisphere of the brain enters a sleep state while the other remains awake. The waking hemisphere lies on the opposite side to the sleeping one and keeps the animal moving, surfacing to breathe and aware of its surroundings. It may also help a dolphin maintain contact with the rest of its group. Because the alert hemisphere can detect unusual sounds or movements, a sleeping dolphin can still respond to predators or other threats in the water. This ability is especially important for marine mammals, which cannot stop swimming and breathing for long. This pattern is one of the clearest signs that sleep does not always require whole-brain shutdown.

Birds also use a form of unihemispheric sleep, often keeping one eye open and the opposite side of the brain alert. This is thought to help them detect approaching danger while resting. Some long-distance seabirds are known to obtain brief bouts of sleep while airborne, using one hemisphere at a time as they glide over the ocean. The amount of sleep obtained in flight is much less than on land, but it may be enough to prevent severe sleep loss during days spent at sea. Scientists have confirmed this by attaching small recording devices to seabirds on long flights over the ocean.

Total sleep time varies dramatically. At one extreme, some small insect-eating bats may sleep for nearly twenty hours a day, while large grazing mammals such as giraffes may manage only a few hours. Although body size and diet play a part, predation risk and feeding requirements are two of the most important influences. Animals that are hunted by many predators must remain alert, while those that feed on low-energy plant material often need to spend long hours eating. Predators themselves, by contrast, can frequently afford to sleep more. Body size and diet shape sleep, but they do not act alone; an animal's age and the time of year can also shift its needs.

Sleep should not be confused with hibernation or daily torpor, which are different forms of energy saving. During torpor an animal's body temperature falls sharply, its heart rate slows and its metabolism is strongly reduced. Unlike sleep, torpor can last for days or weeks and is usually a response to cold, heat or food shortage. An animal may emerge from torpor still needing ordinary sleep, which suggests that the two states serve separate functions. Laboratory work with small mammals supports this view, since they still show sleep pressure after leaving torpor.

Outside mammals and birds, sleep-like states have been identified in a wide range of animals. Fish often become quiet and unresponsive at particular times of day, while reptiles and amphibians show periods of reduced activity. A sleep-like state has also been identified in insects such as fruit flies, which become immobile and harder to rouse. These findings suggest that the basic need for rest evolved very early, long before the appearance of mammals and birds. The type of rest seen in these animals may not involve the same brain patterns found in mammals and birds, but it meets the broad definition of sleep.

Research into animal sleep has practical implications. Many species are exposed to artificial light, noise and human activity that can disrupt their rest, and protected areas may need to be managed with sleep in mind. At the same time, studying unusual sleep patterns may help scientists understand the functions of sleep in humans. Comparing species that sleep very little with those that sleep much more could eventually reveal which aspects of sleep are essential and which are flexible. Some research groups are now collecting data on sleep in wild animals, using small movement loggers and brain recorders. These advances may help test long-standing ideas about sleep.

Companion animals are now a familiar part of daily life, and headlines routinely promise that owning a dog or cat can lower stress, protect the heart and even add years to a person's life. The popular claims made for pet ownership often race ahead of the evidence, however. Although some benefits are real, many studies are small, short-term or poorly controlled, and the health effects of living with an animal are more complicated than public discussion suggests. In my view, pets can contribute to wellbeing, but the scale and certainty of that contribution have been consistently overstated.

The clearest physical benefit is probably increased activity. Dog owners in particular tend to walk more than people without dogs, and this regular, moderate exercise may improve fitness and help with weight control. Walking a dog also brings people into contact with neighbours and other dog walkers, creating brief but repeated social exchanges. These interactions can reduce feelings of isolation and may help older people remain engaged with their local community. The effect is not automatic, of course, because some owners simply let a dog into the garden, but the potential is well documented.

Companion animals are also valued for their psychological effects. Stroking a cat or dog can lower self-reported stress, and the presence of an animal may provide comfort during painful or frightening experiences. Some studies have found reductions in loneliness among people who live alone with pets, and animal-assisted therapy is used in hospitals, care homes and schools. These subjective benefits matter, but they are hard to measure independently of the person's prior expectations and circumstances, and they may not translate into long-term changes in health.

The main difficulty is that most research in this field is observational and cannot establish cause and effect. People who choose to own pets may differ from people who do not in many ways, including income, housing, physical health and personality, and those differences may explain apparent health effects. When researchers find that pet owners have lower blood pressure, for example, this is an association, not proof that pet ownership caused the improvement. In addition, studies with negative or weak results are less likely to be published, so the published record may give an exaggerated picture.

The limits of the evidence are illustrated by the question of heart disease. A major heart association reviewed the research and concluded that pet ownership, especially dog ownership, may be linked to lower cardiovascular risk, but that the evidence is not strong enough to recommend acquiring a pet solely for cardiovascular health. Media reports sometimes convert this cautious conclusion into a claim that pets protect the heart. In reality, any benefit is likely to be indirect, operating through exercise, regular routines and social contact rather than through some mysterious effect of the animal itself.

Studies of children have produced similarly mixed messages. Some research has reported that early contact with cats and dogs protects against allergies and asthma, while other studies have found no such effect or even the opposite. The conflicting results may reflect differences in timing, genetics and environment, but they mean that parents cannot rely on pet ownership as a way to prevent allergic disease. Any decision to bring an animal into a household should therefore be based on a family's wishes and ability to care for the animal, not on unsupported medical promises.

Pets also carry risks that are rarely discussed in upbeat media stories. Animals can transmit infections to people, and some of these zoonotic diseases are serious, especially for pregnant women, young children and people with weakened immune systems. Dogs may cause falls or bites, and cats can transmit toxoplasmosis, a parasitic infection that can harm an unborn child. Reptiles and young birds can carry salmonella, which is why hygiene is essential after handling them. Hospitals that allow therapy animals must therefore screen the animals and manage infection risks carefully.

The strongest evidence concerns social connection, not dramatic medical cures. Interactions with a pet can provide companionship, create a daily routine and give people a sense of being needed. For many older adults, a dog or cat is not a medical treatment but a reason to get up in the morning. This is a genuine benefit, but it says more about loneliness and social ties than about pharmacology. The challenge for researchers is to separate the effects of the animal from the effects of simply caring for another living creature.

Public debate about pets and health would benefit from greater caution. Pets are not medical devices, and their value cannot be reduced to a list of clinical outcomes. At the same time, the responsibilities of ownership, including cost, time, housing and the animal's own welfare, are often ignored when people acquire animals for purported health reasons. I do not doubt that many people are happier and more active with a companion animal, but that is a matter of individual circumstances, not a universal prescription.