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  3. You should spend about 20 minutes on Questions 14-26 which are based on Reading Passage 2 below. What if everything had a barcod

You should spend about 20 minutes on Questions 14-26 which are based on Reading Passage 2 below. What if everything had a barcod

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问题 You should spend about 20 minutes on Questions 14-26 which are based on Reading Passage 2 below.
What if everything had a barcode?
A vast new database will let us catalogue every plant and animal on the planet, and identify them in seconds.
Imagine going for a walk and spotting a wild flower. Its beauty and fragrance delight you, but the name eludes you. No problem. You whip out a hand-held scanner, about the size of a mobile phone, and pop a fragment of a leaf into the device. A few seconds, and the read-out tells you that you’re looking at a pyramidal orchid. Satisfied, you continue on your way.
Sound far-fetched? Not at all. Scientists are currently creating a DNA barcode for every species of plant and animal on the planet It won’t be long before everyone, from experts to amateurs, will be able to scan the world’s flora and fauna as if they were checking out groceries at a supermarket, to look up or confirm their identities.
There are numerous practical uses too. Such a device would let you scan fish at the fishmonger’s to check if it’s been labelled properly, work out exactly what is in your mixed vegetable soup, and confirm whether a piece of furniture really has come from a renewable forest, as the retailer claims. It would also assist forensic science teams, who could quickly identify the pollen on a suspect, to link him to a particular location; customs officials, in their efforts to prevent disease-carrying pests being taken across national borders; and environmental inspectors assessing water quality, who need to work out what microbes are lurking in a particular sample.
It was Professor Paul Hebert, a biologist from the University of Guelph in Canada, who came up with the idea of DNA barcoding the natural world. The inspiration came while he was walking up and down the aisles of a supermarket, marvelling at the ability of the store to keep track of all the lines stocked and sold using the thick and thin lines that make up a barcode. Could scientists, he wondered, exploit a barcode system to record the millions of species on earth via their DNA?
The compilation of a planetary inventory began more than 250 years ago, with the Swedish life classifier Carl Linnaeus. In 1758, he founded the science of taxonomy — a method of classifying living things — based on physical and behavioural characteristics. To date, scientists have classified about 1.7 million organisms, a small fraction of the total number of species, which has been estimated at anywhere between 5 and 30 million. But taxonomy is difficult and time-consuming. Many species, such as the different kinds of flies, look remarkably similar. Only an expert who has spent years examining a particular group can distinguish one from another. Even the experts may be stumped, however, when presented with an egg, an embryo, a seedling or a root. The next problem is that we are running out of time in which to complete the inventory. The International Union for the Conservation of Nature estimates that a quarter of the world’s population of mammals are threatened with extinction.
So, Hebert’s idea centred on finding a fragment of DNA that would disclose the identity of a species without having to decode its entire genetic code. He envisaged a ’DNA barcode reader’, similar to the scanners at retail checkouts. Outlining his idea in Scientific American, Hebert writes: ’An inspector at a busy seaport, a hiker on a mountain trail, or a scientist in a lab could insert a sample containing DNA — a snippet of whisker, say, or the leg of an insect — into the device, which would detect the sequence of nucleic acids in the barcode segment. This information would be instantly relayed to a reference database, a public library of DNA barcodes. Anyone, anywhere, could identify species.’
To create the barcode, Hebert proposed the use of a section of DNA, from the energy-producing units found in all cells. He selected a gene that gives rise to an enzyme known as COL This gene is small enough to be quickly and easily deciphered, but has sufficient variation for us to be able to tell most animal species apart. You and I, for instance, will have different versions of CO1, but they will be similar enough to show that we’re both humans and not chimpanzees.
In 2003, Hebert and his team published their first results. They showed that the barcode system could identify the group an animal came from (for example, whether it was a vertebrate, a worm or an insect) and even the species when it was stored in the barcode library. After years of work, results indicate that animals can now be identified by their barcodes in 98 per cent of cases. Early results have confirmed the additional benefits of the new system: for example, caterpillars of the tropical butterfly Astraptes fulgerator, which was first recognised as a species in 1775, all look very similar, and were assumed to belong to a single species. Barcoding has shown there are 10 different kinds.
Of course, the value of the system depends on a comprehensive reference library of the DNA (COl) barcodes of established species. The Barcode of Life Data systems is an enormous international collaboration supported by 150 institutions in 45 countries. To date, it has compiled more than 500,000 records from 50,000 species. The consortium is hoping that the world’s birds will be barcoded in the next three years. ’People have watched birds for so long that they might think every different tweet has been heard, every different colour observed, but barcoding may prove otherwise,’ says Professor Mark Stoeckle, professor of the human environment at Rockefeller University, New York, who works with Hebert. He estimates that out of the world’s 10,000 bird species, DNA barcoding will distinguish at least 1,000 new ones.
Questions 14-18
Do the following statements agree with the information given in Reading Passage 2?
In boxes 14-18 on your answer sheet, write
TRUE if the statement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this
A large number of new bird species have already been identified by the DNA barcode system.
选项 A、TRUE
B、FALSE
C、NOT GIVEN
答案B
解析 由new bird species可定位至末段最后一句。该句提到鉴定出新鸟类品种是估计出来的(estimates)，用的是将来时will distinguish，说明动作尚未完成，而题目用的是现在完成时have already been identified，题目错在时态错误，故答案为FALSE。
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