IELTS Reading Practice Test 5: Free, with Answers

AAlmost everything we eat depends on a surprisingly small number of plants, and on the genetic variety within them. For thousands of years, farmers saved seed from their best plants and exchanged it with their neighbours, producing countless local varieties, each adapted to its own soil, climate and pests. In the twentieth century much of this variety disappeared, as farmers around the world switched to a few high-yielding modern varieties. According to one widely quoted estimate from the Food and Agriculture Organization of the United Nations, around three-quarters of the genetic diversity of crops was lost in the course of the century. This matters because the old varieties often carry genes for resisting drought, heat or disease, which plant breeders may need in the future.

BThe first person to collect crop varieties systematically was the Russian botanist Nikolai Vavilov. Between the 1920s and the late 1930s, he led more than a hundred expeditions across five continents, gathering seeds from markets, fields and remote mountain villages. He was convinced that each crop had a 'centre of origin', a region where its wild relatives grew and where its diversity was greatest, and that these were the places to search for useful genes. By the end of the 1930s, his institute in Leningrad held what was then the largest seed collection in the world. Vavilov himself did not live to see its value recognised: he was arrested in 1940, during a political campaign against his ideas, and died in prison three years later.

CThe collection faced its most severe test during the Second World War. For almost 900 days, from 1941 to 1944, Leningrad was surrounded by German forces, and hundreds of thousands of its inhabitants died of hunger. The seeds remained in the city, where they were threatened not only by bombs but also by rats and by desperate citizens searching for food. The institute's staff took turns to guard the stores, and several of them died of starvation at their desks rather than eat the rice, wheat and potatoes they were protecting. Thanks to their sacrifice, most of the collection survived, and it is still used by plant breeders today.

DModern seed banks rely on a simple principle: most seeds can survive for a very long time if they are dried and kept cold. Seeds are first dried until only a small amount of moisture remains, then sealed in airtight packets and stored at around minus twenty degrees Celsius. Under these conditions, the seeds of many crops will remain alive for decades, and some for centuries. However, not all plants cooperate. The seeds of some species, including avocado, cocoa and many tropical trees, are killed by drying, and therefore cannot be stored in this way. For these so-called recalcitrant seeds, scientists are developing alternative methods, such as freezing tiny pieces of the plant in liquid nitrogen.

EMost seed banks concentrate on crops, but the Millennium Seed Bank, which is run by the Royal Botanic Gardens, Kew, and was opened in 2000 in the south of England, has a different aim: to conserve wild plants, especially those that are rare, threatened or useful to local people. Working with partners in around a hundred countries, it now holds more than two billion seeds from over 40,000 species. Because a frozen seed gives no outward sign of whether it is still alive, samples are taken out at regular intervals and tested to see whether they will still germinate.

FThe best-known seed bank of all, however, has no collection of its own. The Svalbard Global Seed Vault, opened in 2008 on a remote Norwegian island far inside the Arctic Circle, is a backup for other seed banks, which send copies of their samples to be stored there. The vault is cut deep into a mountainside, in permanently frozen ground, and is kept at minus eighteen degrees; even if the cooling equipment failed, the surrounding rock would keep the seeds frozen for many years. The seeds remain the property of the organisations that deposit them, and the boxes are never opened by the vault's staff. In 2016, unusually warm weather caused meltwater to enter the entrance tunnel. No seeds were damaged, but the incident led to major improvements to the entrance.

GIn 2015 the vault proved its worth. The International Center for Agricultural Research in the Dry Areas, known as ICARDA, had kept its main gene bank near Aleppo in Syria, but the civil war made it impossible to continue working there. Using the copies it had deposited in Svalbard, the centre was able to grow new seed in Lebanon and Morocco and so rebuild its collection, later sending fresh copies back to the Arctic. Yet some scientists warn that seed banks have a weakness: a frozen seed does not evolve. While plants growing in farmers' fields continue to adapt to new pests and a changing climate, those in storage stay exactly as they were. For this reason, many experts argue that seed banks should support, rather than replace, the work of farmers who keep traditional varieties alive by growing them.

The lecture is among the oldest teaching methods still in widespread use. It dates from the medieval universities of Europe, where books were copied by hand and were so expensive that few students could afford them; the lecturer, whose title derives from the Latin word for 'reader', read the text aloud while students wrote it down. Eight centuries later, the printing press, the textbook and the internet have made that original purpose obsolete, yet the format has proved remarkably durable. In universities across the world, a single speaker addressing a hall of several hundred silent students remains the standard way of introducing a subject. Critics argue that this represents an expensive institutional habit which the available evidence no longer supports. In my view, they are largely right about the evidence, but wrong about what should be done.

The most influential evidence comes from a review published in 2014 by the biologist Scott Freeman and his colleagues, who combined the results of 225 studies of university courses in science, engineering and mathematics. In courses taught mainly by traditional lecturing, students were one and a half times more likely to fail than in courses that used 'active learning', in which students spend part of each class solving problems, discussing questions or explaining ideas to one another. Average examination scores were also considerably higher in the active classes. The authors concluded, provocatively, that if the comparison had been a trial of a new medicine, it would have been stopped early, because continuing to give the less effective treatment to one group of patients would have been unethical. It is difficult to dismiss findings drawn from so many different courses and institutions.

Why, then, do lectures survive? Part of the answer is simply cost: one lecturer can teach five hundred students at once, and it would be dishonest to pretend that this plays no part in universities' decisions. Nor do I believe that it is necessarily wrong for it to do so, since resources are limited, and money saved on large classes can pay for small-group teaching elsewhere. A more interesting part of the answer, however, concerns students themselves. Many students genuinely prefer lectures, and they consistently rate them highly in satisfaction surveys. A study carried out at Harvard University in 2019 suggests that this preference may be misleading. Students on an introductory physics course were taught some topics through polished lectures and others through active sessions, all delivered by experienced instructors. When they were tested, they had learned more in the active sessions, yet they believed they had learned more from the lectures. The effort of working through problems, the researchers argued, felt like a sign of confusion, whereas a fluent explanation produced a comfortable but false sense of understanding.

If students' impressions are an unreliable guide, so too are some of the arguments made by the lecture's critics. It is frequently claimed, for example, that students can concentrate for only ten to fifteen minutes before their attention fades. This figure is repeated in countless publications on university teaching, but when the psychologists Karen Wilson and James Korn traced it back to its sources in 2007, they found that the original studies were few in number and poorly designed, and that they did not support any such precise limit. Attention certainly varies during a lecture, but it seems to depend far more on what the lecturer is doing than on the clock.

A careful reading of the research also suggests that the real problem is not the lecture as such. As long ago as 1971, in a book entitled What's the Use of Lectures?, the British educational researcher Donald Bligh reviewed the evidence then available and concluded that lectures were about as effective as other methods for passing on information, but considerably less effective at stimulating thought or changing attitudes. What makes a traditional lecture ineffective, in other words, is that students are passive for an hour at a time, listening and copying rather than thinking.

It follows that abolishing lectures altogether, as some reformers propose, would be a mistake. A skilled lecturer can still provide something that is difficult to obtain elsewhere: a clear overview of a subject, showing how its parts fit together and why they matter, delivered by someone whose enthusiasm is often infectious. What needs to change is the way in which the time is used. A lecture can be interrupted at intervals by questions that every student must answer, perhaps by voting on their phones, before the lecturer explains the correct answer; alternatively, students can be asked to discuss a problem with their neighbours for a few minutes. Such techniques require almost no additional resources, and they can be used in a hall of five hundred as easily as in a seminar room of twenty.

None of these changes will happen automatically, however. Lecturers who were themselves taught by traditional methods may feel uncomfortable about giving up control of the room, and students who are accustomed to listening quietly may at first resist being asked to work. Universities that are serious about teaching will therefore need to support their staff in making the change. But the real choice is not between the lecture and its abolition. It is between lectures that ask nothing of students and lectures that make them think.