Questões de Inglês

ZEBRAS

Lesley Evans Ogden 

[1]   Why zebras have stripes has long perplexed naturalists and continues to challenge scientists. Among the proposed explanations are that stripes promote social cohesion, regulate temperature, or confuse predators and biting flies. The matter, however, is far from settled.

[2]   Ecologist Brenda Larison of the University of California, Los Angeles, and six colleagues decided to have a fresh look at three hypotheses: predator evasion, thermoregulation, and biting fly avoidance. Plains zebras, Equus quagga, show a marked geographic variation in their stripes, which range from heavy black-and-white patterns covering the entire body to thinner, lighter stripes restricted to particular areas. For example, a now extinct subspecies from South Africa, E. q. quagga, had stripes on its neck, head, and torso but not on its belly or legs. The difference from region to region prompted the team to search for associations between environmental factors and striping patterns.

[3]   The researchers chose sixteen populations of plains zebras and photographed a minimum of eight animals per site. Using image-processing software, they noted the number of stripes and their length, thickness, and color saturation on the legs, torso, and belly. They also gathered data on twenty-nine environmental variables, including temperature, precipitation, soil moisture, leaf water content, and tree canopy cover. In addition, they used the Food and Agricultural Organization’s published distribution of tsetse flies and modeled the historic geographic distribution of lions and tsetse flies. The team then ran a computer model and looked at which variables best predicted the observed geographic variation of stripes.

[4]   Surprisingly, they found no clear link between striping patterns and escape from predators or avoidance of biting flies. Instead, temperature was the strongest predictor of stripe variation. Plains zebras living in warmer regions had thicker, more defined stripes than those in cooler regions. This, say the authors, seems to support the idea that contrasting black and white stripes lead to differential air currents, potentially giving the zebras an onboard air conditioner. Such a mechanism has previously been proposed but still remains to be investigated directly. Another untested possibility is that it’s not tsetse fly distribution that matters, but rather the distribution of the disease-causing parasites carried by the flies. “It’s something I want to follow up on,” says Larison, who is also studying the genetics that underlies zebra striping.

[5]   “We usually think about zebra stripes in terms of benefits of striping, but the fact that they lose their striping in certain areas suggests that perhaps there are also some costs,” she says. The mystery of zebra stripes is still being resolved, but for now, one possible explanation has been seriously considered.

Adapted from Natural History, March 2015.

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Vast majority of certain Amazon communities suffer from mercury poisoning

March 30, 2016

  The indigenous communities living in the northern Brazilian and southern Venezuelan parts of the Amazon are suffering from mercury poisoning.

  According to a study, almost all of the water and food sources in the specific part of the Amazon is contaminated with mercury. The researchers took hair samples from the indigenous people living in the region and found out that over ninety percent of the people living in the 19 Yanomami and Yekuana communities there, are suffering from mercury poisoning.

  The main reason behind the mercury poisoning is the numerous illegal mining activities taking place in the Amazon. The study suggests that the mercury comes from illegal gold mines operating in the region, which pollute rivers during the gold extraction process. However, the diet of the people living in the Amazon relies on the rivers as they drink river water and mainly feed with river fishes.

(https://neurope.eu. Adaptado.)

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Vast majority of certain Amazon communities suffer from mercury poisoning

March 30, 2016

  The indigenous communities living in the northern Brazilian and southern Venezuelan parts of the Amazon are suffering from mercury poisoning.

  According to a study, almost all of the water and food sources in the specific part of the Amazon is contaminated with mercury. The researchers took hair samples from the indigenous people living in the region and found out that over ninety percent of the people living in the 19 Yanomami and Yekuana communities there, are suffering from mercury poisoning.

  The main reason behind the mercury poisoning is the numerous illegal mining activities taking place in the Amazon. The study suggests that the mercury comes from illegal gold mines operating in the region, which pollute rivers during the gold extraction process. However, the diet of the people living in the Amazon relies on the rivers as they drink river water and mainly feed with river fishes.

(https://neurope.eu. Adaptado.)

Leia o texto para responder à questão.

Vast majority of certain Amazon communities suffer from mercury poisoning

March 30, 2016

  The indigenous communities living in the northern Brazilian and southern Venezuelan parts of the Amazon are suffering from mercury poisoning.

  According to a study, almost all of the water and food sources in the specific part of the Amazon is contaminated with mercury. The researchers took hair samples from the indigenous people living in the region and found out that over ninety percent of the people living in the 19 Yanomami and Yekuana communities there, are suffering from mercury poisoning.

  The main reason behind the mercury poisoning is the numerous illegal mining activities taking place in the Amazon. The study suggests that the mercury comes from illegal gold mines operating in the region, which pollute rivers during the gold extraction process. However, the diet of the people living in the Amazon relies on the rivers as they drink river water and mainly feed with river fishes.

(https://neurope.eu. Adaptado.)

Leia o texto para responder à questão.

Vast majority of certain Amazon communities suffer from mercury poisoning

March 30, 2016

  The indigenous communities living in the northern Brazilian and southern Venezuelan parts of the Amazon are suffering from mercury poisoning.

  According to a study, almost all of the water and food sources in the specific part of the Amazon is contaminated with mercury. The researchers took hair samples from the indigenous people living in the region and found out that over ninety percent of the people living in the 19 Yanomami and Yekuana communities there, are suffering from mercury poisoning.

  The main reason behind the mercury poisoning is the numerous illegal mining activities taking place in the Amazon. The study suggests that the mercury comes from illegal gold mines operating in the region, which pollute rivers during the gold extraction process. However, the diet of the people living in the Amazon relies on the rivers as they drink river water and mainly feed with river fishes.

(https://neurope.eu. Adaptado.)

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Rare animals vital for ecosystem life support

  Rare animal species are vital to maintaining tropical ecosystems and could cause a chain reaction of disastrous biodiversity loss if they go extinct, a study warns.

  Animals that are considered rare – because they occupy a niche environment or there are few of them – are more likely than common animals to perform specialised and often irreplaceable roles in their environments, the study found. This is especially true for highly biodiverse environments, such as the tropics, the researchers say. “Losing rare species today may mean losing much more complex processes in the long term,” says lead author Rafael Leitão, a biologist at the National Institute of Amazonian Research in Manaus, Brazil.

  The study notes that rare animals perform essential “ecosystem services” such as dispersing seeds, filtering water and controlling other animal populations and invasive species. “There is no way to know exactly how, in future, an ecosystem     11     with the loss of those rare species, but chain effects are common, meaning that the loss of some functions can lead to other losses, making the whole environment crumble,” says Leitão.

(www.scidev.net. Adaptado.)