IELTSwithJurabek

PASSAGE 2

Read the text and answer questions 14-26

Will Eating Less Make You Live Longer?

The latest in a conflicting series of studies suggests calorie restriction could potentially slow ageing in humans

A Calorie restriction, or 'semi-starvation' as some refer to it, has been proven to extend lifespan in many living organisms from yeast to mice, but the picture for primates, including humans, is not so clear. Research published by a team at the University of Wisconsin in the United States shows that rhesus monkeys also live longer on a calorie-restricted diet. But those findings disagree with research by the National Institute on Aging (NIA) in Maryland, also in the United States. Rozalyn Anderson, of the Wisconsin team, says the research is not intended as a recommendation of calorie restriction. 'I find the idea monumentally unattractive!' she says. 'We study it because it is so effective at delaying ageing and the onset of age-related disease. It's a way to tease out what it is that creates increased disease vulnerability as a function of age.'

B Both groups started long-term trials on rhesus monkeys in the late 1980s to determine whether calorie restriction would extend the lifespan of primates. In mice, many experiments had come to the same finding: feed them a diet with 30% fewer calories and see a lifespan extension of 40%. The monkey trials were set up in a similar way: researchers took the calorie content of a standard monkey diet, cut it by 30% (while continuing to supply all essential nutrients) and monitored whether those monkeys lived longer, healthier lives than those on the standard diet.

C In 2009, with the monkeys approaching old age, preliminary findings of the two trials started coming in. For the Wisconsin monkeys, calorie restriction seemed to be working. Compared to well-fed control animals, the lean monkeys were living longer and suffering less from the diseases of ageing: diabetes, heart disease and brain diseases. However, in 2012 the NIA results emerged with a dramatically different conclusion: their monkeys were not living any longer than the controls, although they were healthier.

D The Wisconsin group's latest results confirm that their calorie-restricted monkeys are living longer than the controls. They also offer a possible explanation of why the two groups' findings don't agree, and that lies in the treatment of the control group. The Wisconsin study began with monkeys in early adulthood. Initially, all the monkeys were allowed to eat as much as they liked. A few months into the trial, the monkeys were placed into one of two groups: the controls (who continued to be fed as much as they wished) and the calorie-restricted monkeys (who were given an individualised diet of 30% less than they were previously eating).

E The NIA study differed in two ways. First, the control group of monkeys were not allowed to eat as much as they wished. They were given a diet considered to represent a normal calorie count, while the calorie-restricted monkeys were fed 30% less than that. Second, whereas the Wisconsin monkeys were given highly processed food high in sucrose, making it easy to standardise, the NIA diet was based on whole grains, fish oils, and was very low in sugar. These different settings for the normal control diet may provide an explanation of why the two groups showed different results.

F The Wisconsin group may in effect have studied the effects of 'overeating'. Their control animals weighed up to 10% more than average for their age and gender. Compared to them, the calorie-restricted animals not only suffered fewer diseases, they lived longer. Julie Mattison, head of the NIA study, observes that an overweight person who goes to a fast food restaurant every day will obviously benefit if their calories are cut back by 30%.

G The NIA study fed their control monkeys what they considered a 'standard' caloric intake and saw that longevity for monkeys that were fed 30% less was the same. But in Anderson's view, the NIA control monkeys were not fed enough; the NIA was calorie restricting both groups of animals. Their older female control monkeys, for example, weighed nearly 20% less than the national average. Indeed, Anderson points out that several of the NIA control monkeys have lived past the age of 40, far exceeding the 27-year average lifespan for captive rhesus monkeys. 'That's the maximum lifespan ever detected for the species, so the idea that their intervention is doing nothing is really at odds with the data,' says Anderson.

H However, neither group had the right notion of a standard diet according to Leonie Heilbronn, who researches calorie restriction and healthy ageing at the University of Adelaide in Australia. Heilbronn points out that the NIA controls were a very healthy set of monkeys and leaner than a control monkey should be. On the other hand, she notes, the Wisconsin controls were a little bigger than they had to be. On balance, Heilbronn agrees with the Wisconsin researcher's argument. 'I think these studies suggest calorie restriction definitely will increase lifespan,' she says.

I Both studies agree that cutting calories is beneficial to health - in both cases the calorie-restricted monkeys had fewer diseases related to ageing. As to the question of whether calorie restriction extends lifespan in primates, Anderson and Mattison are currently working together to compare the two studies' raw data. They plan to co-publish a joint analysis. The current data conflict will ultimately provide deeper insights into ageing, Anderson predicts. 'The fact the two studies were set up differently, asking the same question in different ways - I think we will gain maximally from that.'

PASSAGE 3

Read the text and answer questions 27-40

Saving the Skink

What can be done to save the skink, one of New Zealand's most endangered lizards?

A New Zealand's reptiles come in three forms: the tuatara, the geckos and the skinks. With their gleaming scales, long bodies and often surprisingly short limbs, skinks are instantly recognisable. There are more than 90 species, half of which still await formal description. Identification depends on where specimens are found, and such minutiae as the number of scales on their toes. Two of the largest species of skink - the grand and the Otago - are found only in Otago, in New Zealand's South Island. Skinks, being reptiles, need to regulate their temperature, and lie on sunny rocks to absorb heat. However, the grand and Otago are the only kinds that do not hibernate through winter; when snow can fall even in summer in Otago, there is no point in them lying dormant for extended periods. Like all other New Zealand reptiles except tuatara and the egg-laying Suter's skink, they give birth to tiny baby lizards. Today, the Otago and grand skinks are lucky to reach five years of age in the wild, although in zoos or research centres they can live beyond thirty.

B Unfortunately, extinction may loom for these reptiles. With any decline in New Zealand fauna, predation is always suspected, so the efforts of the Department of Conservation (DOC) have focused on controlling specific pests. An example was a six-year project to control the feral cats on the Otago Skink Reserve, launched in the 1990s. Despite the capture of hundreds of cats, skinks showed no signs of recovery; indeed, there were further declines. The trapping programme also revealed rats and hedgehogs to be predators.

C Parasite infections are also thought to be on the rise. Although no direct health implications have been detected the trend is a concern, as it may signal a subtle deterioration in the skinks' living environment. Infection with mites is suspected of inhibiting reproduction among captive animals.

D Another potential threat is habitat loss. Eight hundred years ago, Otago was covered in forest. However, extensive burning produced wide open tussock country. The skinks' response to this change isn't known, nor what their habitat was in the earlier environment, with its predominance of shrubs and trees. Furthermore, recent intensive farming has led to poor soil. Even if we had the answer to the eradication of predators, we haven't a clue to the habitat we should be recreating for the skinks, or if where they persist is best for conservation.

E It is also puzzling that grands and Otagos are disappearing more rapidly than other species in the same region. The explanation likely lies in their delayed sexual maturity. Taking five years before you can breed is a handicap, since there is little likelihood of surviving that long. If survivors have only two offspring annually, they do little to remedy the situation. The commoner skinks mature earlier and produce more offspring, thereby doing more to counter predator pressure. Not that there is room for complacency concerning these species. As more is learned about the size of skink populations, it becomes clear that even common species may be facing a doubtful future.

F So far, DOC's efforts to eliminate specific predators have not resulted in a recovery of skink numbers. The prediction that less than six years is all the Otagos and grands have left is supported by data from surveys conducted outside the protected area between 1984 and 2002. These show that more than 50 per cent of sub-populations of both skinks have died out over the past years. Populations in other regions are believed to be smaller, although access issues on some properties limit knowledge. No more than five years remain in which to turn things around - a close call considering it will be at least three before detectable response in the populations can be expected owing to their low breeding rate.

G DOC's recovery-programme team has recently embarked upon an experiment to extend nearly two kilometres of mammal-proof fencing around a population of Otagos and grands in the Macraes Flat reserve. Choosing a site was difficult, as with a limited budget and the high cost of the fencing it had to be small. It also had to include vacant space and resources for a growing population. An added complication was that grands and Otagos have subtly different environmental preferences, both of which need catering for.

H Because of the danger of imminent extinction, the team has also had to develop emergency captive-management techniques. Specially permitted breeders, who have had some success in breeding the Otago in captivity, are now developing techniques to breed grands. Captive management, however, is a last resort. The priority is to manage and protect skinks in the wild.

I Getting the public to understand the plight of these creatures is essential. Without public support, their chances are slim. Conservation is as much driven by public opinion as it is by political decisions. In New Zealand, the situation is more pressing than just about anywhere else on the planet because many of its native birds and lizards have simply not evolved to defend themselves against species introduced in the last few hundred years. In the once-isolated islands that form New Zealand, ecosystem collapse didn't happen 5000 years ago or even 500 years ago; it's happening now.

J Fortunately, DOC no longer faces these problems alone. The challenge has been taken up by a group of conservationists representing business, science and agriculture. Central Otago Ecological Trust (COET) aims to establish a refuge for the reintroduction of native species. It has identified suitable habitat and, with the generous support of a local farmer with grazing land there, has begun the construction of a mammal-proof fence to protect a 24-hectare area. The recovery programme and COET provide hope that skinks might once again flourish.