READING PASSAGE 6
Biological control of pests
The continuous and reckless use of synthetic chemicals for the control of pests which pose a threat to agricultural crops and human health is proving to be counterproductive. Apart from engendering widespread ecological disorders, pesticides have contributed to the emergence of a new breed of chemical-resistant, highly lethal superbugs.
According to a recent study by the Food and Agriculture Organisation (FAO), more than 300 species of agricultural pests have developed resistance to a wide range of potent chemicals. Not to be left behind are the disease-spreading pests, about 100 species of which have become immune to a variety of insecticides now in use.
One glaring disadvantage of pesticides’ application is that, while destroying harmful pests, they also wipe out many useful non-targeted organisms, which keep the growth of the pest population in check. This results in what agroecologists call the ‘treadmill syndrome’. Because of their tremendous breeding potential and genetic diversity, many pests are known to withstand synthetic chemicals and bear offspring with a built-in resistance to pesticides.
The havoc that the ‘treadmill syndrome’ can bring about is well illustrated by what happened to cotton farmers in Central America. In the early 1940s, basking in the glory of chemical-basedintensive agriculture, the farmers avidly took to pesticides as a sure measure to boost crop yield. The insecticide was applied eight times a year in the mid-1940s, rising to 28 in a season in the mid-1950s, following the sudden proliferation of three new varieties of chemical-resistant pests.
By the mid-1960s, the situation took an alarming turn with the outbreak of four more new pests, necessitating pesticide spraying to such an extent that 50% of the financial outlay on cotton production was accounted for by pesticides. In the early 1970s, the spraying frequently reached 70 times a season as the farmers were pushed to the wall by the invasion of genetically stronger insect species.
Most of the pesticides in the market today remain inadequately tested for properties that cause cancer and mutations as well as for other adverse effects on health, says a study by United States environmental agencies.
The United States National Resource Defense Council has found that DDT was the most popular of a long list of dangerous chemicals in use.
In the face of the escalating perils from indiscriminate applications of pesticides, a more effective and ecologically sound strategy of biological control, involving the selective use of natural enemies of the pest population, is fast gaining popularity - though, as yet, it is a new field with limited potential. The advantage of biological control in contrast to other methods is that it provides a relatively low-cost, perpetual control system with a minimum of detrimental side-effects. When handled by experts, bio-control is safe, non-polluting and self-dispersing.
The Commonwealth Institute of Biological Control (CIBC) in Bangalore, with its global network of research laboratories and field stations, is one of the most active, noncommercial research agencies engaged in pest control by setting natural predators against parasites. CIBC also serves as a clearing-house for the export and import of biological agents for pest control world-wide.
CIBC successfully used a seed-feeding weevil, native to Mexico, to control the obnoxious parthenium weed,known to exert devious influence on agriculture and human health in both India and Australia. Similarly the Hyderabad-based Regional Research Laboratory (RRL), supported by CIBC, is now trying out an Argentinian weevil for the eradication of water hyacinth, another dangerous weed, which has become a nuisance in many parts of the world. According to Mrs Kaiser Jamil of RRL, ‘The Argentinian weevil does not attack any other plant and a pair of adult bugs could destroy the weed in 4-5 days.’ CIBC is also perfecting the technique for breeding parasites that prey on ‘disapene scale’ insects - notorious defoliants of fruit trees in the US and India.
How effectively biological control can be pressed into service is proved by the following examples. In the late 1960s, when Sri Lanka’s flourishing coconut groves were plagued by leaf-mining hispides, a larval parasite imported from Singapore brought the pest under control. A natural predator indigenous to India, Neodumetia sangawani, was found useful in controlling the Rhodes grass-scale insect that was devouring forage grass in many parts of the US. By using Neochetina bruci, a beetle native to Brazil, scientists at Kerala Agricultural University freed a 12-kilometre-long canal from the clutches of the weed Salvinia molesta, popularly called‘African Payal’ in Kerala. About 30,000 hectares of rice fields in Kerala are infested by this weed.
Questions 14-17 (Choose the correct letter, A, B, C, or D).
17 The use of pesticides has contributed to
A a change in the way ecologies are classified by agroecologists.
B an imbalance in many ecologies around the world.
C the prevention of ecological disasters in some parts of the world.
D an increase in the range of ecologies which can be usefully farmed.
18 The Food and Agriculture Organisation has counted more than 300 agricultural pests which
A are no longer responding to most pesticides in use.
B can be easily controlled through the use of pesticides.
C continue to spread disease in a wide range of crops.
D may be used as part of bio-control’s replacement of pesticides.
19 Cotton farmers in Central America began to use pesticides
A because of an intensive government advertising campaign.
B in response to the appearance of new varieties of pest.
C as a result of changes in the seasons and the climate.
D to ensure more cotton was harvested from each crop.
20 By the mid-1960s, cotton farmers in Central America found that pesticides
A were wiping out 50% of the pests plaguing the crops.
B were destroying 50% of the crops they were meant to protect.
C were causing a 50% increase in the number of new pests reported.
D were costing 50% of the total amount they spent on their crops.
READING PASSAGE 7
The psychology of innovation
Why are so few companies truly innovative?
Innovation is key to business survival，and companies put substantial resources into inspiring employees to develop new ideas. There are, nevertheless, people working in luxurious, state-of-the-art centres designed to stimulate innovation who find that their environment doesn’t make them feel at all creative. And there are those who don’t have a budget, or much space, but who innovate successfully.
For Robert B. Cialdini, Professor of Psychology at Arizona State University, one reason that companies don’t succeed as often as they should is that innovation starts with recruitment. Research shows that the fit between an employee’s values and a company’s values makes a difference to what contribution they make and whether,two years after they join, they’re still at the company. Studies at Harvard Business School show that, although some individuals may be more creative than others, almost every individual can be creative in the right circumstances.
One of the most famous photographs in the story of rock’n’roll emphasises Ciaidini’s views. The 1956 picture of singers Elvis Presley, Carl Perkins, Johnny Cash and Jerry Lee Lewis jamming at a piano in Sun Studios in Memphis tells a hidden story. Sun’s ‘million-dollar quartet’ could have been a quintet. Missing from the picture is Roy Orbison’ a greater natural singer than Lewis, Perkins or Cash. Sam Phillips, who owned Sun,wanted to revolutionise popular music with songs that fused black and white music, and country and blues.
Presley, Cash, Perkins and Lewis instinctively understood Phillips’s ambition and believed in it. Orbison wasn’t inspired by the goal, and only ever achieved one hit with the Sun label.
The value fit matters, says Cialdini, because innovation is, in part, a process of change, and under that pressure we, as a species, behave differently, ‘When things change, we are hard-wired to play it safe.’ Managers should therefore adopt an approach that appears counterintuitive -they should explain what stands to be lost if the company fails to seize a particular opportunity. Studies show that we invariably take more gambles when threatened with a loss than when offered a reward.
Managing innovation is a delicate art. It’s easy for a company to be pulled in conflicting directions as the marketing, product development, and finance departments each get different feedback from different sets of people. And without a system which ensures collaborative exchanges within the company, it’s also easy for small ‘pockets of innovation‟ to disappear. Innovation is a contact sport. You can‟t brief people just by saying,‘We’re going in this direction and I’m going to take you with me.’
Cialdini believes that this ‘follow-the-leader syndrome, is dangerous, not least because it encourages bosses to go it alone. ‘It’s been scientifically proven that three people will be better than one at solving problems, even if that one person is the smartest person in the field.’ To prove his point, Cialdini cites an interview with molecular biologist James Watson. Watson, together with Francis Crick, discovered the structure of DNA, the genetic information carrier of all living organisms. ‘When asked how they had cracked the code ahead of an array of highly accomplished rival investigators, he said something that stunned me. He said ”he and Crick had succeeded because they were aware that they weren’t the most intelligent of the scientists pursuing the answer.
The smartest scientist was called Rosalind Franklin who, Watson said, “was so intelligent she rarely sought advice”.’
Teamwork taps into one of the basic drivers of human behaviour. ‘The principle of social proof is so pervasive that we don’t even recognise it,’ says Cialdini. ‘If your project is being resisted, for example, by a group of veteran employees, ask another old-timer to speak up for it.’ Cialdini is not alone in advocating this strategy. Research shows that peer power, used horizontally not vertically, is much more powerful than any boss’s speech.
Writing, visualising and prototyping can stimulate the flow of new ideas. Cialdini cites scores of research papers and historical events that prove that even something as simple as writing deepens every individual’s engagement in the project. It is, he says, the reason why all those competitions on breakfast cereal packets encouraged us to write in saying, in no more than 10 words: ‘I like Kellogg’s Com Flakes because… .’ The very act of writing makes us more likely to believe it.
Authority doesn’t have to inhibit innovation but it often does. The wrong kind of leadership will lead to what Cialdini calls ”captain is, the regrettable tendency of team members to opt out of team responsibilities that are properly their’. He calls it captain is because, he says, ”crew members of multipilot aircraft exhibit a sometimes deadly passivity when the flight captain makes a clearly wrong-headed decision”. This behaviour is not, he says, unique to air travel, but can happen in any workplace where the leader is overbearing.
At the other end of the scale is the 1980s Memphis design collective, a group of young designers for whom”the only rule was that there were no rule”. This environment encouraged a free interchange of ideas, which led to more creativity with form, function, colour and materials that revolutionised attitudes to furniture design.
Many theorists believe the ideal boss should lead from behind, taking pride in collective accomplishment and giving credit where it is due. Cialdini says:”Leaders should encourage everyone to contribute and simultaneously assure all concerned that every recommendation is important to making the right decision and will be given full attention” The frustrating thing about innovation is that there are many approaches, but no magic formula. However, a manager who wants to create a truly innovative culture can make their job a lot easier by recognising these psychological realities.
Questions 27-30
Choose the correct letter, A, B, C or D.
28. The example of the ‘million-dollar quartet’ underlines the writer’s point about
A recognising talent.
B working as a team.
C having a shared objective.
D being an effective leader.
29. James Watson suggests that he and Francis Crick won the race to discover the DNA code because they
A were conscious of their own limitations.
B brought complementary skills to their partnership.
C were determined to outperform their brighter rivals.
D encouraged each other to realise their joint ambition.
30. The writer mentions competitions on breakfast cereal packets as an example of how to
A inspire creative thinking.
B generate concise writing.
C promote loyalty to a group.
D strengthen commitment to an idea.
31. In the last paragraph, the writer suggests that it is important for employees to
A be aware of their company's goals.
B feel that their contributions are valued.
C have respect for their co-workers‟achievements.
D understand why certain management decisions are made.
READING PASSAGE 8
Museums of fine art and their public
The fact that people go to the Louvre museum in Paris to see the original painting Mona Lisa when they can see a reproduction anywhere leads us to question some assumptions about the role of museums of fine art in today’s world One of the most famous works of art in the world is Leonardo da Vinci’s Mona Lisa. Nearly everyone who goes to see the original will already be familiar with it from reproductions, but they accept that fine art is more rewardingly viewed in its original form.
However, if Mona Lisa was a famous novel, few people would bother to go to a museum to read the writer’s actual manuscript rather than a printed reproduction. This might be explained by the fact that the novel has evolved precisely because of technological developments that made it possible to print out huge numbers of texts, whereas oil paintings have always been produced as unique objects. In addition, it could be argued that the practice of interpreting or ‘reading’ each medium follows different conventions. With novels, the reader attends mainly to the meaning of words rather than the way they are printed on the page, whereas the ‘reader’of a painting must attend just as closely to the material form of marks and shapes in the picture as to any ideas they may signify.
Yet it has always been possible to make very accurate facsimiles of pretty well any fine art work. The seven surviving versions of Mona Lisa bear witness to the fact that in the 16th century, artists seemed perfectly content to assign the reproduction of their creations to their workshop apprentices as regular ‘bread and butter’work. And today the task of reproducing pictures is incomparably more simple and reliable, with reprographic techniques that allow the production of high-quality prints made exactly to the original scale, with faithful colour values, and even with duplication of the surface relief of the painting.
But despite an implicit recognition that the spread of good reproductions can be culturally valuable, museums continue to promote the special status of original work.
Unfortunately, this seems to place severe limitations on the kind of experience offered to visitors.One limitation is related to the way the museum presents its exhibits. As repositories of unique historical objects, art museums are often called ‘treasure houses’. We are reminded of this even before we view a collection by the presence of security guards, attendants, ropes and display cases to keep us away from the exhibits. In many cases, the architectural style of the building further reinforces that notion. In addition,a major collection like that of London’s National Gallery is housed in numerous rooms, each with dozens of works, any one of which is likely to be worth more than all the average visitor possesses. In a society that judges the personal status of the individual so much by their material worth, it is therefore difficult not to be impressed by one’s own relative ‘worthlessness’ in such an environment.
Furthermore, consideration of the ‘value’ of the original work in its treasure house setting impresses upon the viewer that, since these works were originally produced, they have been assigned a huge monetary value by some person or institution more powerful than themselves. Evidently, nothing the viewer thinks about the work is going to alter that value, and so today’s viewer is deterred from trying to extend that spontaneous,immediate, self-reliant kind of reading which would originally have met the work.
The visitor may then be struck by the strangeness of seeing such diverse paintings, drawings and sculptures brought together in an environment for which they were not originally created. This ‘displacement effect’ is further heightened by the sheer volume of exhibits. In the case of a major collection, there are probably more works on display than we could realistically view in weeks or even months.
This is particularly distressing because time seems to be a vital factor in the appreciation of all art forms.A fundamental difference between paintings and other art forms is that there is no prescribed time over which a painting is viewed. By contrast, the audience encourage an opera or a play over a specific time, which is the duration of the performance. Similarly novels and poems are read in a prescribed temporal sequence, whereas a picture has no clear place at which to start viewing, or at which to finish. Thus art works themselves encourage us to view them superficially, without appreciating the richness of detail and labour that is involved.
Consequently, the dominant critical approach becomes that of the art historian, a specialised academic approach devoted to ‘discovering the meaning’ of art within the cultural context of its time. This is in perfect harmony with the museum s function, since the approach is dedicated to seeking out and conserving ‘authentic’, original, readings of the exhibits. Again, this seems to put paid to that spontaneous, participators criticism which can be found in abundance in criticism of classic works of literature, but is absent from most art history.
The displays of art museums serve as a warning of what critical practices can emerge when spontaneous criticism is suppressed. The museum public, like any other audience, experience art more rewardingly when given the confidence to express their views. If appropriate works of fine art could be rendered permanently accessible to the public by means of high-fidelity reproductions, as literature and music already are, the public may feel somewhat less in awe of them. Unfortunately, that may be too much to ask from those who seek to maintain and control the art establishment.
Questions 32-35 (Choose the correct letter, A, B, C or D).
32. The writer mentions London’s National Gallery to illustrate
A the undesirable cost to a nation of maintaining a huge collection of art.
B the conflict that may arise in society between financial and artistic values.
C the negative effect a museum can have on visitors’ opinions of themselves.
D the need to put individual well-being above large-scale artistic schemes.
33. The writer says that today, viewers may be unwilling to criticise a because
A they lack the knowledge needed to support an opinion.
B they fear it may have financial implications.
C they have no real concept of the work’s value.
D they feel their personal reaction is of no significance.
34. According to the writer, the ‘displacement effect’ on the visitor is caused by
A the variety of works on display and the way they are arranged.
B the impossibility of viewing particular works of art over a long period.
C the similar nature of the paintings and the lack of great works.
D the inappropriate nature of the individual works selected for exhibition.
35. The writer says that unlike other forms of art, a painting does not
A involve direct contact with an audience.
B require a specific location for a performance.
C need the involvement of other professionals.
D have a specific beginning or end.
READING PASSAGE 9
Beyond the blue horizon
Ancient voyagers who settled the far-flung islands of the Pacific Ocean
(1)An important archaeological discovery on the island of Efate in the Pacific archipelago of Vanuatu has revealed traces of an ancient seafaring people, the distant ancestors of todays, Polynesians. The site came to light only by chance. An agricultural worker, digging in the grounds of a derelict plantation, scraped open a grave – the first of dozens in a burial ground some 3,000 years old. It is the oldest cemetery ever found in the Pacific islands, and it harbors the remains of an ancient people archaeologists call the Lapita.
(2)
They were daring blue-water adventurers who used basic canoes to rove across the ocean. But they were not just explorers. They were also pioneers who carried with them everything they would need to build new lives –their livestock, taro seedlings and stone tools. Within the span of several centuries, the Lapita stretched the boundaries of their world from the jungle-clad volcanoes of Papua New Guinea to the loneliest coral outliers of Tonga.
(3)
The Lapita left precious few clues about themselves, but Efate expands the volume of data available to researchers dramatically. The remains of 62 individuals have been uncovered so far, and archaeologists were also thrilled to find six complete Lapita pots. Other items included a Lapita burial urn with modeled birds arranged on the rim as though peering down at the human remains sealed inside. ‘It’s an important discovery,’ says Matthew Spriggs, professor of archaeology at the Australian National University and head of the international team digging up the site, ‘for it conclusively identifies the remains as Lapita.’
(4)
DNA teased from these human remains may help answer one of the most puzzling questions in Pacific anthropology: did all Pacific islanders spring from one source or many? Was there only one outward migration from a single point in Asia, or several from different points? ‘This represents the best opportunity we’ve had yet,’ says Spriggs, ‘to find out who the Lapita actually were, where they came from, and who their closest descendants are today.’
(5)
There is one stubborn question for which archaeology has yet to provide any answers: how did the Lapita accomplish the ancient equivalent of a moon landing, many times over? No-one has found one of their canoes or any rigging, which could reveal how the canoes were sailed. Nor do the oral histories and traditions of later Polynesians offer any insights, for they turn into myths long before they reach as far back in time as the Lapita.
(6)
‘All we can say for certain is that the Lapita had canoes that were capable of ocean voyages, and they had the ability to sail them,’ says Geoff Irwin, a professor of archaeology at the University of Auckland. Those sailing skills, he says, were developed and passed down over thousands of years by earlier mariners who worked their way through the archipelagoes of the western Pacific, making short crossings to nearby islands. The real adventure didn’t begin, however, until their Lapita descendants sailed out of sight of land, with empty horizons on every side. This must have been as difficult for them as landing on the moon is for us today. Certainly it distinguished them from their ancestors, but what gave them the courage to launch out on such risky voyages?
(7)
The Lap it as thrust into the Pacific was eastward, against the prevailing trade winds, Irwin notes. Those nagging headwinds, he argues, may have been the key to their success. ‘They could sail out for days into the unknown and assess the area, secure in the knowledge that if they didn’t find anything, they could turn about and catch a swift ride back on the trade winds. This is what would have made the whole thing work.’ Once out there, skilled seafarers would have detected abundant leads to follow to land: seabirds, coconuts and twigs carried out to sea by the tides, and the afternoon pile-up of clouds on the horizon which often indicates an island in the distance.
(8) For returning explorers, successful or not, the geography of their own archipelagoes would have provided a safety net. Without this to go by, overshooting their home ports, getting lost and sailing off into eternity would have been all too easy. Vanuatu, for example, stretches more than 500 miles in a northwest-southeast trend, its scores of inrervisible islands forming a backstop for mariners riding the trade winds home.
(9)
All this presupposes one essential detail, says Atholl Anderson, professor of prehistory at the Australian National University: the Lapita had mastered the advanced art of sailing against the wind. ‘And there’s no proof they could do any such thing,’ Anderson says. ‘There has been this assumption they did, and people have built canoes to re-create those early voyages based on that assumption. But nobody has any idea what their canoes looked like or how they were rigged.
(10)
Rather than give all the credit to human skill, Anderson invokes the winds of chance. El Nino, the same climate disruption that affects the Pacific today, may have helped scatter the Lapita, Anderson suggests. He points out that climate data obtained from slow-growing corals around the Pacific indicate a series of unusually frequent El Ninos around the time of the Lapita expansion. By reversing the regular east-to-west flow of the trade winds for weeks at a time, these super El Ninos might have taken the Lapita on long unplanned voyages.
(11)
However they did it, the Lapita spread themselves a third of the way across the Pacific, then called it quits for reasons known only to them. Ahead lay the vast emptiness of the central Pacific and perhaps they were too thinly stretched to venture farther. They probably never numbered more than a few thousand in total, and in their rapid migration eastward they encountered hundreds of islands – more than 300 in Fiji alone.
Questions 36-39
36 According to the writer, there are difficulties explaining how the Lapita accomplished their journeys because
A the canoes that have been discovered offer relatively few clues.
B archaeologists have shown limited interest in this area of research.
C little information relating to this period can be relied upon for accuracy.
D technological advances have altered the way such achievements are viewed.
37 According to the sixth paragraph, what was extraordinary about the Lapita?
A They sailed beyond the point where land was visible.
B Their cultural heritage discouraged the expression of fear.
C They were able to build canoes that withstood ocean voyages.
D Their navigational skills were passed on from one generation to the next.
38 What does ‘This’ refer to in the seventh paragraph?
A the Lapita’s seafaring talent
B the Lapita s ability to detect signs of land
C the Lapita’s extensive knowledge of the region
D the Lapita’s belief they would be able to return home
39 According to the eighth paragraph, how was the geography of the region significant?
A It played an important role in Lapita culture.
B It meant there were relatively few storms at sea.
C It provided a navigational aid for the Lapita.
D It made a large number of islands habitable.
READING PASSAGE 10
When evolution runs backwards
Evolution isn’t supposed to run backwards - yet an increasing number of examples show that it does and that it can sometimes represent the future of a species.
The description of any animal as an ‘evolutionary throwback’ is controversial. For the better part of a century,most biologists have been reluctant to use those words, mindful of a principle of evolution that says ‘evolution cannot run backwards. But as more and more examples come to light and modern genetics enters the scene,that principle is having to be rewritten. Not only are evolutionary throwbacks possible, they sometimes play an important role in the forward march of evolution.
The technical term for an evolutionary throwback is an ‘atavism’, from the Latin atavus, meaning forefather.The word has ugly connotations thanks largely to Cesare Lombroso, a 19th-century Italian medic who argued that criminals were born not made and could be identified by certain physical features that were throwbacks to a primitive, sub-human state.
While Lombroso was measuring criminals, a Belgian palaeontologist called Louis Dollo was studying fossil records and coming to the opposite conclusion. In 1890 he proposed that evolution was irreversible: that ‘an organism is unable to return, even partially, to a previous stage already realised in the ranks of its ancestors. Early 20th-century biologists came to a similar conclusion, though they qualified it in terms of probability, stating that there is no reason why evolution cannot run backwards -it is just very unlikely. And so the idea of irreversibility in evolution stuck and came to be known as ‘Dollo’s law.
If Dollo’s law is right, atavisms should occur only very rarely, if at all. Yet almost since the idea took root,exceptions have been cropping up. In 1919, for example, a humpback whale with a pair of leglike appendages over a metre long, complete with a full set of limb bones, was caught off Vancouver Island in Canada.Explorer Roy Chapman Andrews argued at the time that the whale must be a throwback to a land-living ancestor. ‘I can see no other explanation, he wrote in 1921.
Since then, so many other examples have been discovered that it no longer makes sense to say that evolution is as good as irreversible. And this poses a puzzle: how can characteristics that disappeared millions of years ago suddenly reappear?
In 1994, Rudolf Raff and colleagues at Indiana University in the USA decided to use genetics to put a number on the probability of evolution going into reverse. They reasoned that while some evolutionary changes involve the loss of genes and are therefore irreversible, others may be the result of genes being switched off. If these silent genes are somehow switched back on, they argued, longlost traits could reappear.
Raff’s team went on to calculate the likelihood of it happening. Silent genes accumulate random mutations,they reasoned, eventually rendering them useless. So how long can a gene survive in a species if it is no longer used? The team calculated that there is a good chance of silent genes surviving for up to 6 million years in at least a few individuals in a population, and that some might survive as long as 10 million years. In other words, throwbacks are possible, but only to the relatively recent evolutionary past.
As a possible example, the team pointed to the mole salamanders of Mexico and California. Like most amphibians these begin life in a juvenile ‘tadpole’ state, then metamorphose into the adult form – except for one species, the axolotl, which famously lives its entire life as a juvenile. The simplest explanation for this is that the axolotl lineage alone lost the ability to metamorphose, while others retained it. From a detailed analysis of the salamanders’ family tree, however, it is clear that the other lineages evolved from an ancestor that itself had lost the ability to metamorphose. In other words, metamorphosis in mole salamanders is an atavism. The salamander example fits with Raff’s 10million-year time frame.
More recently, however, examples have been reported that break the time limit, suggesting that silent genes may not be the whole story. In a paper published last year, biologist Gunter Wagner of Yale University reported some work on the evolutionary history of a group of South American lizards called Bachia. Many of these have minuscule limbs; some look more like snakes than lizards and a few have completely lost the toes on their hind limbs. Other species, however, sport up to four toes on their hind legs. The simplest explanation is that the toed lineages never lost their toes, but Wagner begs to differ. According to his analysis of the Bachia family tree, the toed species re-evolved toes from toeless ancestors and, what is more, digit loss and gain has occurred on more than one occasion over tens of millions of years.
So what’s going on? One possibility is that these traits are lost and then simply reappear, in much the same way that similar structures can independently arise in unrelated species, such as the dorsal fins of sharks and killer whales. Another more intriguing possibility is that the genetic information needed to make toes somehow survived for tens or perhaps hundreds of millions of years in the lizards and was reactivated. These atavistic traits provided an advantage and spread through the population, effectively reversing evolution.
But if silent genes degrade within 6 to million years, how can long-lost traits be reactivated over longer timescales? The answer may lie in the womb. Early embryos of many species develop ancestral features.
Snake embryos, for example, sprout hind limb buds. Later in development these features disappear thanks to developmental programs that say ‘lose the leg’. If for any reason this does not happen, the ancestral feature may not disappear, leading to an atavism.
Questions 40
40. When discussing the theory developed by Louis Dollo, the writer says that
A it was immediately referred to as Dollo’s law.
B it supported the possibility of evolutionary throwbacks.
C it was modified by biologists in the early twentieth century.
D it was based on many years of research.
41. The humpback whale caught off Vancouver Island is mentioned because of
A the exceptional size of its body.
B the way it exemplifies Dollo’s law.
C the amount of local controversy it caused.
D the reason given for its unusual features.
42. What is said about ‘silent genes’?
A Their numbers vary according to species.
B Raff disagreed with the use of the term.
C They could lead to the re-emergence of certain characteristics.
D They can have an unlimited life span.
43. The writer mentions the mole salamander because
A. it exemplifies what happens in the development of most amphibians.
B. it suggests that Raffs theory is correct.
C. it has lost and regained more than one ability.
D. its ancestors have become the subject of extensive research.
44. Which of the following does Wagner claim?
A Members of the Bachia lizard family have lost and regained certain features several times.
B Evidence shows that the evolution of the Bachia lizard is due to the environment.
C His research into South American lizards supports Raffs assertions.
D His findings will apply to other species of South American lizards.
Answers
19 A
20 B
21 C
22 A
23 C
24 B
25 A
26 D
27 D
28 C
29 A
30 D
31 B
32 C
33 D
34 A
35 D
36 C
37 A
38 D
39 C
40 C
41 D
42 C
43 B
44 A
