IELTS Reading Test 122

A For a stalking predator, the element of surprise is crucial. And for jumping spiders that sneak onto other spiders’ webs to prey on their owners, it can be the difference between having lunch and becoming it. Now zoologists have discovered the secret of these spiders’ tactics: creeping forward when their prey’s web is vibrating. B The fifteen known species of Portia jumping spiders are relatively small, with adults being about two centimeters long (that’s smaller than the cap on most pens). They habitually stay in the webs of other spiders, and in an area of these webs that is as out-of-the-way as possible. Portia spiders live mostly in tropical forests, where the climate is hot and humid. They hunt a range of other spiders, some of which could easily turn the tables on them. ‘They will attack something about twice their own size if they are really hungry,’ says Stimson Wilcox of Binghamton University in New York State. Wilcox and his colleague, Kristen Gentile of the University of Canterbury in Christchurch, New Zealand, wanted to find out how Portia spiders keep the upper hand. C All jumping spiders have large eyes that look like binocular lenses, and they function pretty much the same way. Most jumping spiders locate their prey visually, and then jump and capture from one centimeter to over ten centimeters away. Only a few species of jumping spiders invade the webs of other spiders, and the Portia spider is among them. Jumping spiders, including Portia spiders, prey on insects and other arthropods by stalking. Sometimes the spiders lure their victims by vibrating the web to mimic the struggles of a trapped insect. But many web-weaving spiders appear to be wise to these tricks, so stalking is often a better strategy. Sometimes, the researchers found, Portia spiders take advantage of the vibrations created in the web by a gentle breeze. But if necessary, they will make their own vibrations. D The researchers allowed various prey spiders to spin webs in the laboratory and then introduced Portia spiders. To simulate the shaking effect of a breeze the zoologists used either a model aircraft propeller or attached a tiny magnet to the centre of the web which could be vibrated by applying a varying electrical field. The researchers noticed that the stalking Portia spiders moved more when the webs were shaking than when they were stilt and they were more likely to capture their prey during tests in which the webs were penorncally shaken than in those where the webs were undisturbed. If the spiders were placed onto unoccupied webs, they would make no attempt to change their movements. E It is the Portia spider’s tactic of making its victims’ webs shake that has most intrigued the researchers, They noticed that the spiders would sometimes shake their quarry’s web violently, then creep forwards up to five millimeters before the vibrations died down. ‘They’d make a big pluck with one of their hind legs,’ says Wilcox. These twangs were much more powerful than the gentler vibrations Portia spiders use to mimic a trapped insect, and the researchers were initially surprised that the prey spiders did not respond to them in any way. But they have since discovered that the violent twanging produces a pattern of vibrations that match those caused by a twig falling onto the web. F Other predators make use of natural ‘smokescreens’ or disguise to hide from their prey: lions hunting at night, for example, move in on their prey when clouds obscure the moon. ‘But this is the first example of an animal making its own smokescreen that we know of,’ says Wilcox. ‘Portia spiders are clearly intelligent and they often learn from their prey as they are trying to capture it. They do this by making different signals on the web of their prey until the prey spider makes a movement. In general, Portia spiders adjust their stalking strategy according to their prey and what the prey is doing. Thus, Portia spiders use trial-and-error learning in stalking. Sometimes they will even take an indirect route to reach a prey spider they can see from a distance. This can sometimes take one to two hours following a predetermined route. When it does this, the Portia spider is actually solving problems and thinking ahead about its actions.’

A Conditions in the working environment of Western countries changed significantly over the 20th century. Though not without some associated problems, these changes may be viewed generally as positive: child labour all but ceased, wages rose, the number of working hours in a week decreased, pension policies became standard, fringe benefits multiplied and concerns over health and safety issues were enforced. B The collection of data relating to work conditions also became a far more exact science. In particular, there were important developments in methodology and data gathering. Additionally, there was a major expansion of the data collection effort – more people became involved in learning about the workplace; and, for the first time, results started to be published. This being the case, at the end of the century, not only were most workers better off than their early 20th century predecessors had been, but they were also in a position to understand how and why this was the case. By carefully analyzing the statistical data made available, specific changes in the workplace – not least regarding the concept of what “work” should involve – became clearly discernible. C The most obvious changes to the workplace involved the size and composition of the countries’ workforces. Registering only 24 million in 1900 (and including labourers of age ten and up) and 139 million (aged 16 and older), the size of America’s workforce, for instance, increased by almost six-fold – in line with its overall population growth. At the same time, the composition of the workforce shifted from industries dominated by primary production occupations, such as farmers and foresters, to those dominated by professional, technical and, in particular, service workers. At the beginning of the 20th century, 38% of all American workers were employed on farms, by the end of the same century, that figure had fallen to less than 3 %. D In Europe, much the same process occurred. In the 1930’s, in every European country, bar Britain and Belgium, more than 20 per cent of the population worked in agriculture. By the 1980’s, however, the farming populations of all developed countries, excluding Eastern Europe, had dropped to ten per cent and often even lower. At the same time, capital intensive farming using highly mechanized techniques dramatically reduced the numbers needed to farm there. E And therein lay the problem. While the workplace became a safer and more productive environment, a world away from the harsh working conditions of our forefathers, the switch from an agricultural to a modern working environment also created massive unemployment in many countries. Fundamental to this problem was the widespread move from the countryside to the city. Having lost their livelihoods, the world’s peasant populations amassed in ever larger numbers in already crowded communities, where rates of job growth failed to keep up with internal migration. As a result, thousands were left squatting in shanty towns on the periphery of cities, waiting for jobs that might never arrive. While this was (and is) particularly true of Third World countries, the same phenomenon could also be witnessed in several American, French, English and German cities in the late 20th century. F From a different and more positive perspective, in the 20th century, women became visible and active members of all sectors of the Western workplace. In 1900, only 19% of European women of working age participated in the labour force; by 1999, this figure had risen to 60%. In 1900, only 1% of the country’s lawyers and 6% of its physicians were female; by contrast, the figures were 29% and 24% in 1999. A recent survey of French teenagers, both male and female, revealed that over 50% of those polled thought that, in any job (bar those involving military service), women make better employees, as they are less likely to become riled under stress and less overtly competitive than men. G The last and perhaps most significant change to the 20th-century workplace involved the introduction of technology. The list of technological improvements in the workplace is endless: communication and measuring devices, computers of all shapes and sizes, x-ray, lasers, neon lights, stainless steel, and so on and on. Such improvements led to a more productive, safer work environment. Moreover, the fact that medicine improved so dramatically led to an increase in the average lifespan among Western populations. In turn, workers of very different ages were able to work shoulder to shoulder, and continue in their jobs far longer. H By the end of 20th century, the Western workplace had undergone remarkable changes. In general, both men and women worked fewer hours per day for more years under better conditions. Yet, the power of agriculture had waned as farmers and foresters moved to cities to earn greater salaries as annalists and accountants. For those who could not make this transition, however, life at the dawn of the new century seemed less appealing.