IELTSwithJurabek

You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2.

The Constant Evolution of the Humble Tomato

Heirloom tomatoes - varieties that have been passed down through several generations of a family because they are thought to have a particularly good flavor - are really no more 'natural' than the varieties available in grocery stores. New studies promise to restore their lost, healthy genes.

A Famous for their taste, color and organic appearance, heirloom tomatoes are favorites of gardeners and advocates of locally grown foods. The tomato enthusiast might conclude that, given the immense varieties, heirlooms must have a more diverse and superior set of genes than the tomatoes available in grocery stores, those ordinary hybrid varieties such as cherry and plum. However, their seeming diversity is only skin-deep: heirlooms are actually feeble and inbred - the defective product of breeding experiments that began hundreds of years ago, and exploded thanks to enthusiastic backyard gardeners. 'The irony of all this,' says Steven Tanksley, a geneticist at Cornell University, 'is all that diversity of heirlooms can be accounted for by a handful of genes. There're probably no more than 10 mutant genes that create the diversity of heirlooms you see.' But rather than simply proving that the myth about the heirloom's diversity is wrong, Tanksley's deconstruction of the tomato genome, along with work by others, is showing how a small berry-like fruit from the Andes became one of the world's top crops.

B The cultivated tomato is a member of the nightshade family that includes New World crops such as the potato, which spread around the globe after Christopher Columbus brought them back to Spain in the 15th century. But whereas scientists have uncovered a wealth of archaeological evidence on early farming practices in the New World, the record is blank when it comes to the tomato. The modern tomato seems to have its origins in the Andes in South America, and may have been domesticated in Vera Cruz, Mexico. Primitive varieties still grow throughout the Americas. All told, botanists call as many as 13 species 'tomatoes', and consider an additional four to be closely related.

C One might assume that one of these known wild species became today's cultivated crop, but that's not the case; the Mother Tomato has never been found. The closest relative is the currant tomato which, based on genetic comparisons, split from today's tomato some 1.4 million years ago. So researchers like Tanksley have to work backward, crossing tomato varieties and species in order to understand how various genes influence shape and size. Once isolated, Tanksley later inserts those genes into other tomato varieties to make his case with a dramatic transformation.

D Tanksley concludes from his analyses that in their effort to make bigger, tastier and faster-growing fruit, our ancestors ultimately exploited just 30 mutations out of the tomato's 35,000 genes. Most of these genes have only small effects on tomato size and shape, but recently Tanksley and his colleagues reported that they found a gene that increases fruit size by 50 percent. It was probably the most important event in domestication. The first written record of tomatoes - from Spain in the 1500s - confirms that this mutation, which enlarges tomatoes by producing compartments known as locules, existed back in the same yellow tomatoes that gave Italians the word pomodoro, or golden apple. Besides size, tomato farmers also selected for shape. To discover those genes, Esther van der Knaap, a Tanksley alumnus now at The Ohio State University, took a gene from one heirloom tomato and inserted it into a wild relative. She observed that, as a result, the tiny fruits became shaped like pears.

E The selection of these traits has, however, affected the heirloom's hardiness. They often suffer from infections that cause the fruit to crack, split and otherwise rot quickly. Wild plants must continuously evolve to fend off such infections, points out Roger Chetelat of the Tomato Genetics Resource Center at the University of California. But in their quest for size, shape and flavor, humans have inadvertently eliminated defensive genes. As a result, most possess only a single disease-resistant gene. Chetelat elaborates that heirlooms' taste may have less to do with their genes than with the productivity of the plant and the growing environment. Any plant that produces only two fruits, as heirlooms sometimes do, is highly likely to produce juicier, sweeter and more flavorful fruit than varieties that produce 100, as commercial types do. In addition, heirlooms are sold ripened on the vine, a certain way to get tastier results than allowing them to mature on the shelf. This means breeders feel confident that getting germ-beating genes back into heirlooms won't harm the desirable aspects of the fruit. Modern breeding has resuscitated grocery store tomatoes with an influx of wild genes; in the past 50 years, as many as 40 disease-resistant genes have been bred back into commercial crops.

F In 1996 a tomato breeder and former Tanksley student named Doug Heath began a favorite project. After 12 years of traditional breeding with the help of molecular markers, he created a new multi-colored tomato less prone to cracking and also endowed with 12 disease-resistant genes. The original heirloom plant, Heath explains, had defective flowers, which is one reason why it produced only two fruits compared with the 30 he gets from his new variety. He claims he is also able to maintain a comparable flavor and sugar profile even on productive plants. The heirloom's defects are, after all, just an accident of a narrow breeding strategy left over from the very beginning of genetic modification.

You should spend about 20 minutes on Questions 27-40, which are based on Reading Passage 3 below.

Rewards for scientific achievement

While the Nobel Prizes are over 115 years old, rewards for scientific achievement have been around much longer. As early as the 17th century, at the very origins of modern experimental science, promoters of science realized the need for some system of recognition and reward that would provide incentive for advances in the field.

Before the prize, it was the gift that dominated in science. Precursors to modern scientists - the early astronomers, philosophers, physicians, alchemists and engineers - offered wonderful discoveries, inventions and works of literature or art as gifts to powerful patrons, often royalty. Many scientists prefaced their publications with extravagant letters of dedication; they might, or they might not, be rewarded with a gift in return. Eventually, different kinds of incentives, including prizes and awards, as well as new, salaried academic positions, became more common and the favor of particular wealthy patrons diminished in importance. But at the height of the Renaissance, early scientists relied on gifts from powerful princes to compensate and advertise their efforts.

With courtiers all vying for a patron's attention, scientific gifts had to be presented with drama and flair. The astronomer Galileo Galilei (1564-1642) presented his newly discovered moons of Jupiter to the Medici dukes of Italy as a 'gift' that was literally out of this world. In return, the Medici family 'ennobled' Galileo with the title and position of court philosopher and mathematician. If a gift succeeded, the gift-giver might, like Galileo in this case, be fortunate enough to receive a gift in return. Gift-givers could not, however, predict what form a patron's gift would take, and they might find themselves burdened with offers they couldn't refuse. Tycho Brahe (1546-1601), the great Danish Renaissance astronomer, received everything from exotic animals to chemical secrets in return for his discoveries.

By the early-17th century, scientific promoters realized that gift-giving was ill-suited to encouraging experimental science. Experimentation required many individuals to collect data in many places across long periods of time. Gifts emphasized competitive individualism at a time when scientific collaboration and the often-humdrum work of empirical observation were paramount.

While it was accepted that some competitive rivalry helped to inspire and advance science, scientific reformers believed that too much led to the ostentation that too often plagued courtly giftgiving. Most of all, reformers feared an individual would not tackle a problem that couldn't be finished and presented to a patron in his or her lifetime - or even if they did, their findings might die with them.

For these reasons, promoters of experimental science saw the reform of rewards as integral to radical changes in the pace and scale of scientific discovery. For example, Sir Francis Bacon (1561-1626), lord chancellor of England and an influential booster of experimental science, emphasized the importance even of 'approximations' or unfinished attempts at reaching a particular goal. Instead of dissipating their efforts attempting to appease patrons, many researchers, he hoped, could be stimulated to work toward the same ends via a well-publicized research wish list. Bacon coined the term 'desiderata', still used by researchers today to denote widespread research goals. He also suggested many ingenious ways to advance discovery by stimulating the human hunger for fame; a row of statues celebrating famous inventors of the past, for example, could be paired with a row of empty plinths upon which researchers might imagine their own busts one day resting.

Bacon's techniques inspired one of his chief admirers, the reformer Samuel Hartlib (circa 1600-1662) to collect many schemes for reforming the system of recognition. One proposed that rewards should go not only 'to such as exactly hit the marke, but even to those that probably misse it', because their errors would stimulate others and make 'active braines to beate about for New Inventions'. Hartlib planned a centralized office systematizing rewards for those who 'expect Rewards for Services done to the King or State, and know not where to pitch and what to desire'.

Collaborative scientific societies, beginning in the mid-17th century, distanced rewards from the whims and demands of individual patrons. The periodicals that many new scientific societies started publishing offered a new medium that allowed authors to tackle ambitious research problems that might not individually produce a complete publication pleasing to a dedicatee. The societies saw their periodicals as a means to entice discovery by offering credit. Today's Leopoldina, the German national scientific society, founded its publication in 1670. According to its bylaws, those who might not otherwise publish their findings could see them 'exhibited to the world ... with the praiseworthy mention of their name' - an important step on the way to standardizing scientific citation.

States might also offer rewards for solutions to problems, most famously in the case of the prize offered by the British government in 1714 for figuring out how to determine longitude at sea. Some in the 17th century likened this long-sought discovery to the philosopher's stone. The idea of using a prize to highlight a specific problem is alive and well today. In fact, some contemporary scientific prizes, such as the Simons Foundation's 'Cracking the Glass Problem', set forth specific questions that still need to be resolved.

The shift from gift-giving to prize-giving completely transformed the rules of engagement in scientific discovery. Of course, the need for monetary support hasn't gone away. Obtaining financial support can still be a sizable part of what it takes to get science done today. Succeeding in grant competitions might seem mystifying, and winning a career-changing Nobel might come as a bolt out of the blue. But researchers can take comfort that they no longer have to present their innovations on bended knee as wondrous gifts that will appeal to the whims of individual patrons.