Found a mistake? Let us know! Share this Practice Test. To make political decisions about the extent and type of forestry in a region it is important to understand the consequences of those decisions. One tool for assessing the impact of forestry on the ecosystem is population viability analysis PVA. This is a tool for predicting the probability that a species will become extinct in a particular region over a specific period.

A species becomes extinct when the last individual dies. This observation is a useful starting point for any discussion of extinction as it highlights the role of luck and chance in the extinction process.

To make a prediction about extinction we need to understand the processes that can contribute to it and these fall into four broad categories which are discussed below. Early attempts to predict population viability were based on demographic uncertainty Whether an individual survives from one year to the next will largely be a matter of chance. Some pairs may produce several young in a single year while others may produce none in that same year. Small populations will fluctuate enormously because of the random nature of birth and death and these chance fluctuations can cause species extinctions even if, on average, the population size should increase.

Taking only this uncertainty of ability to reproduce into accountextinction is unlikely if the number of individuals in a population is above about 50 and the population is growing. Small populations cannot avoid a certain amount of inbreeding. This is particularly true if there is a very small number of one sex. For example, if there are only 20 individuals of a species and only one is a maleall future individuals in the species must be descended from that one male.

For most animal species such individuals are less likely to survive and reproduce. Inbreeding increases the chance of extinction.

Variation within a species is the raw material upon which natural selection acts. Without genetic variability a species lacks the capacity to evolve and cannot adapt to changes in its environment or to new predators and new diseases. The loss of genetic diversity associated with reductions in population size will contribute to the likelihood of extinction. Recent research has shown that other factors need to be considered. These fluctuations add yet another degree of uncertainty to the survival of many species.

Catastrophes such as fire, flood, drought or epidemic may reduce population sizes to a small fraction of their average level. When allowance is made for these two additional elements of uncertainty the population size necessary to be confident of persistence for a few hundred years may increase to several thousand.

Beside these processes we need to bear in mind the distribution of a population. A species that occurs in five isolated places each containing 20 individuals will not have the same probability of extinction as a species with a single population of individuals in a single locality. Where logging occurs that is, the cutting down of forests for timber forest- dependent creatures in that area will be forced to leave. Ground-dwelling herbivores may return within a decade.

However, arboreal marsupials that is animals which live in trees may not recover to pre-logging densities for over a century. As more forests are logged, animal population sizes will be reduced further.Jeff Chapman relates the story of history the most important vegetable.

A The potato was first cultivated in South America between three and seven thousand years ago, though scientists believe they may have grown wild in the region as long as 13, years ago. The genetic patterns of potato distribution indicate that the potato probably originated in the mountainous west-central region of the continent.

B Early Spanish chroniclers who misused the Indian word batata sweet potato as the name for the potato noted the importance of the tuber to the Incan Empire.

The Incas had learned to preserve the potato for storage by dehydrating and mashing potatoes into a substance called Chuchu could be stored in a room for up to 10 years, providing excellent insurance against possible crop failures. C The Spanish conquistadors first encountered the potato when they arrived in Peru in in search of gold, and noted Inca miners eating chuchu.

At the time the Spaniards failed to realize that the potato represented a far more important treasure than either silver or gold, but they did gradually begin to use potatoes as basic rations aboard their ships. D Throughout Europe, potatoes were regarded with suspicion, distaste and fear.

Generally considered to be unfit for human consumption, they were used only as animal fodder and sustenance for the starving. In northern Europe, potatoes were primarily grown in botanical gardens as an exotic novelty.

Even peasants refused to eat from a plant that produced ugly, misshapen tubers and that had come from a heathen civilization. E In meat-loving England, farmers and urban workers regarded potatoes with extreme distaste. Inthe Royal Society recommended the cultivation of the tuber to the English government and the nation, but this recommendation had little impact. Potatoes did not become a staple until, during the food shortages associated with the Revolutionary Wars, the English government began to officially encourage potato cultivation.

Gradually, the lower classes began to follow the lead of the upper classes. While the potato slowly gained ground in eastern France where it was often the only crop remaining after marauding soldiers plundered wheat fields and vineyardsit did not achieve widespread acceptance until the late s.

The peasants remained suspicious, in spite of a paper from the Facult de Paris testifying that the potato was not harmful but beneficial. The people began to overcome their distaste when the plant received the royal seal of approval: Louis XVI began to sport a potato flower in his buttonhole, and Marie-Antoinette wore the purple potato blossom in her hair.

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Nearby peasants naturally assumed that anything worth guarding was worth stealing, and so snuck into the field and snatched the plants for their home gardens. H Historians debate whether the potato was primarily a cause or an effect of the huge population boom in industrial-era England and Wales. Few vegetables were consumed, most vegetables being regarded as nutritionally worthless and potentially harmful.

This view began to change gradually in the late s. The Industrial Revolution was drawing an ever increasing percentage of the populace into crowded cities, where only the richest could afford homes with ovens or coal storage rooms, and people were working hour days which left them with little time or energy to prepare food.

I Whereas most of their neighbors regarded the potato with suspicion and had to be persuaded to use it by the upper classes, the Irish peasantry embraced the tuber more passionately than anyone since the Incas. The potato was well suited to the Irish the soil and climate, and its high yield suited the most important concern of most Irish farmers: to feed their families.

Even children could easily plant, harvest and cook potatoes, which of course required no threshing, curing or grinding. The abundance provided by potatoes greatly decreased infant mortality and encouraged early marriage. Julian Bames explores the questions posed by Life-Casts, an exhibition of plaster moulds of living people and objects which were originally used for scientific purposes.

A Art changes over time and our idea of what art is changes too. For example, objects originally intended for devotional, ritualistic or re-creational purposes may be recategorised as art by members of other later civilisations, such as our own, which no longer respond to these purposes. B What also happens is that techniques and crafts which would have been judged inartistic at the time they were used are reassessed. Life-casting is an interesting example of this. It involved making a plaster mould of a living person or thing.

This was complex, technical work, as Benjamin Robert Haydon discovered when he poured litres of plaster over his human model and nearly killed him. At the time, the casts were used for medical research and, consequently, in the nineteenth century life-casting was considered inferior to sculpture in the same way that, more recently, photography was thought to be a lesser art than painting. Both were viewed as unacceptable shortcuts by the "senior" arts.

Their virtues of speed and unwavering realism also implied their limitations; they left little or no room for the imagination. In an infamous lawsuit ofa moulder whose mask of the dying French emperor Napoleon had been reproduced and sold without his permission was judged to have no rights to the image.You should spend about 20 minutes on Questions 40which are based on Reading Passage below.

Honey bees in trouble Can native pollinators fill the gap? Without honeybees, the story goes, fields will be sterile, economies will collapse, and food will be scarce. For one thing, in the United States, where CCD was first reported and has had its greatest impacts, honeybees are not a native species.

The total number of hives involved in the U. For example, honeybee hives can be closed up and moved out of the way when pesticides are applied to a field. The bees are generalist pollinators, so they can be used to pollinate many different crops. And although they are not the most efficient pollinator of every crop, honeybees have strength in numbers, with 20, tobees living in a single hive. Department of Agriculture. The honeybee, in other words, has become a crucial cog in the modem system of industrial agriculture.

That system delivers more food, and more kinds of it, to more places, more cheaply than ever before. But that system is also vulnerable, because making a farm field into the photosynthetic equivalent of a factory floor, and pollination into a series of continent-long assembly lines, also leaches out some of the resilience characteristic of natural ecosystems. D Breno Freitas, an agronomist, pointed out that in nature such a high degree of specialization usually is a very dangerous game: it works well while all the rest is in equilibrium, but runs quickly to extinction at the least disbalance.

In effect, by developing an agricultural system that is heavily reliant on a single pollinator species, we humans have become riskily overspecialized. And when the human-honeybee relationship is disrupted, as it has been by colony collapse disorder, the vulnerability of that agricultural system begins to become clear. E In fact, a few wild bees are already being successfully managed for crop pollination.

For example, about blue orchard bees Osmia lignaria can pollinate a hectare of apples or almonds, a task that would require roughly 50, tohoneybees. There are bee tinkerers engaged in similar work in many comers of the world. In Brazil, Breno Freitas has found that Centris tarsata, the native pollinator of wild cashew, can survive in commercial cashew orchards if growers provide a source of floral oils, such as by interplanting their cashew trees with Caribbean cherry.

Ecologist Rachael Winfree recently led a team that looked at pollination of four summer crops tomato, watermelon, peppers, and muskmelon at 29 farms in the region of New Jersey and Pennsylvania.

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In another study focusing specifically on watermelon, Winfree and her colleagues calculated that native bees alone could provide sufficient pollination at 90 percent of the 23 farms studied. By contrast, honeybees alone could provide sufficient pollination at only 78 percent of farms. In the Delaware Valley, most farms and farm fields are relatively small, each fanner typically grows a variety of crops, and farms are interspersed with suburbs and other types of land use which means there are opportunities for homeowners to get involved in bee conservation, too.

The landscape is a bee-friendly patchwork that provides a variety of nesting habitat and floral resources distributed among different kinds of crops, weedy field margins, fallow fields, suburban neighborhoods, and semi natural habitat like old woodlots, all at a relatively small scale. H Of course, not all farmers will be able to implement all of these practices. And researchers are suggesting a shift to a kind of polyglot agricultural system.

For larger operations, a suite of managed bees—with honeybees filling the generalist role and other, native bees pollinating specific crops—could be augmented by free pollination services from resurgent wild pollinators. Questions Do the following statements agree with the claims of the writer in Reading Passage? In the United States, farmers use honeybees in a large scale over the past few years The blue orchard bee is the most efficient pollinator among native bees for every crop Found a mistake?

Let us know! Share this Practice Test. Besides turning floral nectar into honey, these hardworking insects also pollinate crops for farmers -for a fee. Of the 2, commercial beekeepers in the United States about half migrate This pays off in two ways Moving north in the summer and south in the winter lets bees work a longer blooming season, making more honey — and money — for their keepers.

Second, beekeepers can carry their hives to farmers who need bees to pollinate their crops. Migratory beekeeping is nothing new. The ancient Egyptians moved clay hives, probably on rafts, down the Nile to follow the bloom and nectar flow as it moved toward Cairo.

In the s North American beekeepers experimented with the same idea, moving bees on barges along the Mississippi and on waterways in Florida, but their lighter, wooden hives kept falling into the water. Not until the s when cars and trucks became affordable and roads improved, did migratory beekeeping begin to catch on. For the Californian beekeeper, the pollination season begins in February.

At this time, the beehives are in particular demand by farmers who have almond groves; they need two hives an acre. Most people consider almond honey too bitter to eat so the bees get to keep it for themselves.

By early March it is time to move the bees. It can take up to seven nights to pack the 4, or so hives that a beekeeper may own. These are not moved in the middle of the day because too many of the bees would end up homeless. But at night, the hives are stacked onto wooden pallets, back-to-back in sets of four, and lifted onto a truck. In their new location, the beekeeper will pay the farmer to allow his bees to feed in such places as orange groves. The honey produced here is fragrant and sweet and can be sold by the beekeepers.

These temporary hive extensions contain frames of empty comb for the bees to fill with honey. In the brood chamber below, the bees will stash honey to eat later. To prevent the queen from crawling up to the top and laying eggs, a screen can be inserted between the brood chamber and the supers.

Three weeks later the honey can be gathered. These can then be pulled off the hive. They are heavy with honey and may weigh up to 90 pounds each. The supers are taken to a warehouse. The uncapped frames are put in a carousel that sits on the bottom of a large stainless steel drum. The carousel is filled to capacity with 72 frames. A switch is flipped and the frames begin to whirl at revolutions per minute; centrifugal force throws the honey out of the combs.

Finally the honey is poured into barrels for shipment. After this, approximately a quarter of the hives weakened by disease, mites, or an ageing or dead queen, will have to be replaced. To create new colonies, a healthy double hive, teeming with bees, can be separated into two boxes.

One half will hold the queen and a young, already mated queen can be put in the other half, to make two hives from one. By the time the flowers bloom, the new queens will be laying eggs, filling each hive with young worker bees. The flow chart below outlines the movements of the migratory beekeeper as described in Reading Passage.

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Complete the flow chart. Here the bees make honey. After the honey collection, the old hives are rejected.Found a mistake? Let us know! Share this Practice Test. Air pollution is increasingly becoming the focus of government and citizen concern around the globe. From Mexico City and New York, to Singapore and Tokyo, new solutions to this old problem are being proposed, Mailed and implemented with ever increasing speed.

Action is being taken along several fronts: through new legislation, improved enforcement and innovative technology. Local authorities in London are campaigning to be allowed to enforce anti-pollution lows themselves ; at present only the police have the power to do so, but they tend to be busy elsewhere. In Singapore, renting out toad space to users is the way of the future.

Older cars were the worst offenders; though a sizeable number of quire new cars were also identified as gross polluters, they were simply badly tuned. The aim is to remove the heaviest-polluting, most decrepit vehicles from the roads.

As part of a European Union environmental programme, a London council is resting an infra-red spectrometer from the University of Denver in Colorado. It gauges the pollution from a passing vehicle - more useful than the annual stationary rest that is the British standard today - by bouncing a beam through the exhaust and measuring what gets blocked.

The councils next step may be to link the system to a computerised video camera able to read number plates automatically. The effort to clean up cars may do little to cut pollution if nothing is done about the tendency to drive them more. However, the average number of people in o car on the freeway inwhich is 1.

Increasing it would be an effective way of reducing emissions as well as easing congestion. Electronic innovations make possible increasing sophistication: rates can vary according to road conditions, time of day and so on. Singapore is advancing in this direction, with a city-wide network of transmitters to collect information and charge drivers as they pass certain points. Such road-pricing, however, can be controversial. When the local government in Cambridge, England, considered introducing Singaporean techniques, it faced vocal and ultimately successful opposition.

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Inthe United Nations Environmental Programme and the World Health Organisation WHO concluded that all of a sample of twenty megacities - places likely to have more than ten million inhabitants in the year - already exceeded the level the WHO deems healthy in at least one major pollutant. Two-thirds of them exceeded the guidelines for two, seven for three or more. PM10, a sub-category of particulate matter measuring ten-millionths of a metre across, has been implicated in thousands of deaths a year in Britain alone.

Research being conducted in two counties of Southern California is reaching similarly disturbing conclusions concerning this little- understood pollutant. A world-wide rise in allergies, particularly asthma, over the past four decades is now said to be linked with increased air pollution.

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The lungs and brains of children who grow up in polluted air offer further evidence of its destructive power The old and ill, however, are the most vulnerable to the acute effects of heavily polluted stagnant air. It con actually hasten death, os it did in December when a cloud of exhaust fumes lingered over the city of London for over a week.

The United Nations has estimated that in the year there will be twenty-four mega-cities and a further eighty-five cities of more than three million people. The pressure on public officials, corporations and urban citizens to reverse established trends in air pollution is likely to grow in proportion with the growth of cities themselves.

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Progress is being made. Great thanks to volunteer Ngoc Nguyen has contributed these explanations and question markings. If you want to make a better world like this, please contact us. Look at the following solutions Questions and locations. Match each solution with one location. NB You may use any location more than once.

YES if the statement reflects the claims of the writer.Found a mistake? Let us know! Share this Practice Test. Without honeybees, the story goes, fields will be sterile, economies will collapse, and food will be scarce. For one thing, in the United States, where CCD was first reported and has had its greatest impacts, honeybees are not a native species.

Exam Review

The total number of hives involved in the U. For example, honeybee hives can be closed up and moved out of the way when pesticides are applied to a field. The bees are generalist pollinators, so they can be used to pollinate many different crops.

And although they are not the most efficient pollinator of every crop, honeybees have strength in numbers, with 20, tobees living in a single hive. Department of Agriculture. The honeybee, in other words, has become a crucial cog in the modem system of industrial agriculture. That system delivers more food, and more kinds of it, to more places, more cheaply than ever before. But that system is also vulnerable, because making a farm field into the photosynthetic equivalent of a factory floor, and pollination into a series of continent-long assembly lines, also leaches out some of the resilience characteristic of natural ecosystem s.

D Breno Freitas, an agronomist, pointed out that in nature such a high degree of specialization usually is a very dangerous game: it works well while all the rest is in equilibrium, but runs quickly to extinction at the least disbalance.

In effect, by developing an agricultural system that is heavily reliant on a single pollinator species, we humans have become riskily overspecialized. And when the human-honeybee relationship is disrupted, as it has been by colony collapse disorder, the vulnerability of that agricultural system begins to become clear. E In fact, a few wild bees are already being successfully managed for crop pollination.

For example, about blue orchard bees Osmia lignaria can pollinate a hectare of apples or almondsa task that would require roughly 50, tohoneybees. There are bee tinkerers engaged in similar work in many comers of the world. In Brazil, Breno Freitas has found that Centris tarsata, the native pollinator of wild cashew, can survive in commercial cashew orchards if growers provide a source of floral oils, such as by interplanting their cashew trees with Caribbean cherry.

Ecologist Rachael Winfree recently led a team that looked at pollination of four summer crops tomato, watermelon, peppers, and muskmelon at 29 farms in the region of New Jersey and Pennsylvania.

In another study focusing specifically on watermelon, Winfree and her colleagues calculated that native bees alone could provide sufficient pollination at 90 percent of the 23 farms studied.

By contrast, honeybees alone could provide sufficient pollination at only 78 percent of farms. In the Delaware Valley, most farms and farm fields are relatively small, each fanner typically grows a variety of crops, and farms are interspersed with suburbs and other types of land use which means there are opportunities for homeowners to get involved in bee conservation, too.

The landscape is a bee-friendly patchwork that provides a variety of nesting habitat and floral resources distributed among different kinds of crops, weedy field margins, fallow fields, suburban neighborhoods, and semi natural habitat like old woodlots, all at a relatively small scale.

H Of course, not all farmers will be able to implement all of these practices. And researchers are suggesting a shift to a kind of polyglot agricultural system. For larger operations, a suite of managed bees—with honeybees filling the generalist role and other, native bees pollinating specific crops—could be augmented by free pollination services from resurgent wild pollinators. Great thanks to volunteer Ngoc Nguyen has contributed these explanations and question markings. If you want to make a better world like this, please contact us.

A needs for using pesticides. B impacts of losing insect pollinators. C vulnerabilities of native bees. D benefits in building more pollination industries. A the honeybees can pollinated more crops efficiently. B The bees are semi-domesticated since ancient times.

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C Honeybee hives can be protected away from pesticides. D The ability of wild pollinators using to serve crops declines. A one drawback of the industrialised agricultural system.

B a low cost in modem agriculture.Found a mistake? Let us know! Share this Practice Test. One of the first great intellectual feats of a young child is learning how to talk, closely followed by learning how to count. It is impossible to learn the sequence of events that led to our developing the concept of number. Evidence of early stages of arithmetic and numeration can be readily found. The lack of ability of some cultures to deal with large numbers is not really surprising.

European languages, when traced back to their earlier version, are very poor in number words and expressions. Traces of the very first stages in the development of numeration can be seen in several living languages today. Intermixed with the development of a number sense is the development of an ability to count. All counting ultimately involves reference to something other than the things being counted. Please descibe the mistake as details as possible along with your expected correction, leave your email so we can contact with you when needed.

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Please enter a valid email. Solution for: Numeration Answer Table 1. TRUE 2. FALSE 3. TRUE 5. FALSE 6. TRUE TRUE 7. FALSE Follow us on Facebook Mini ielts. Questions Complete each sentence with the correct ending.

A-Gbelow. A was necessary in order to fulfil a civic role. B was necessary when people began farming. C was necessary for the development of arithmetic. D persists in all societies.

E was used when the range of number words was restricted. F can be traced back to early European languages.


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