首页
登录
职称英语
The world seems increasingly divided into those who favor genetically modifie
The world seems increasingly divided into those who favor genetically modifie
游客
2024-11-08
23
管理
问题
The world seems increasingly divided into those who favor genetically modified (GM) foods and those who fear them. Advocates assert that growing genetically altered crops can be kinder to the environment and that eating foods from those plants is perfectly safe. And, they say, genetic engineering—which can induce plants to grow in poor soils or to produce more nutritious foods—will soon become an essential tool for helping to feed the world’s burgeoning population. Skeptics contend that GM crops could pose unique risks to the environment and to health—risks too troubling to accept placidly. Taking that view, many European countries are restricting the planting and importation of GM agricultural products. Much of the debate hinges on perceptions of safety. But what exactly does recent scientific research say about the hazards?
Advocates of GM, or transgenic, crops say the plants will benefit the environment by requiring fewer toxic pesticides than conventional crops. But critics fear the potential risks and wonder how big the benefits really are. "We have so many questions about these plants, " remarks Guenther Stotzky, a soil microbiologist at New York University. "There’s a lot we don’t know and need to find out."
As GM crops multiply in the landscape, unprecedented numbers of researchers have started fanning into the fields to get the missing information. Some of their recent findings are reassuring; others suggest a need for vigilance.
Every year U.S. growers shower crops with an estimated 971 million pounds of pesticides, mostly to kill insects, weeds and fungi. But pesticide residues linger on crops and the surrounding soil, leaching into groundwater, running into streams and getting gobbled up by wildlife. The constant chemical trickle is an old worry for environmentalists.
In the mid-1990s agribusinesses began advertising GM seeds that promised to reduce a farmer’s use of toxic pesticides. Today most GM crops—mainly soybean, corn, cotton and canola—contain genes enabling them to either resist insect pests or tolerate weed-killing herbicides. The insect-resistant varieties make their own insecticide, a property meant to reduce the need for chemical sprays. The herbicidetolerant types survive when exposed to broad-spectrum weed killers, potentially allowing farmers to forgo more poisonous chemicals that target specific weed species. Farmers like to limit the use of more hazardous pesticides when they can, but GM crops also hold appeal because they simplify operations (reducing the frequency and complexity of pesticide applications) and, in some cases, increase yields.
But confirming environmental benefit is tricky. Virtually no peer-reviewed papers have addressed such advantages, which would be expected to vary from plant to plant and place to place. Some information is available, however. According to the U.S. Department of Agriculture, farmers who plant herbicidetolerant crops do not necessarily use fewer sprays, but they do apply a more benign mix of chemicals. For instance, those who grow herbicide-tolerant soybeans typically avoid the most noxious weed killer, turning instead to glyphosate herbicides, which are less toxic and degrade more quickly.
Insect-resistant crops also bring mixed benefits. To date, insect resistance has been provided by a gene from the soil bacterium Bacillus thuringiensis (Bt). This gene directs cells to manufacture a crystalline protein that is toxic to certain insects—especially caterpillars and beetles that gnaw on crops—but does not harm other organisms. The toxin gene in different strains of Bt. can affect different mixes of insects, so seed makers can select the version that seems best suited to a particular crop.
Defining the environmental risks of GM crops seems even harder than calculating their benefits. At the moment, public attention is most trained on Bt crops, thanks to several negative studies. Regulators, too, are surveying the risks intensely. This spring or summer the EPA is expected to issue major new guidelines for Bt crops, ordering seed producers to show more thoroughly that the crops can be planted safely and monitored in farm fields.
In the face of mounting consumer concern, scientists are stepping up research into the consequences of Bt and other GM crops. Among their questions: How do Bt crops affect "nontarget" organisms—the innocent bugs, birds, worms and other creatures that happen to pass by the modified plants? Will GM crops pollinate nearby plants, casting their genes into the wild to create superweeds that grow unchecked? What are the odds that the genetically engineered traits will lose their ability to protect against insects and invasive weeds, leaving GM plants suddenly vulnerable? [br] What’s the conclusion of the passage towards the controversial issue of GM crops?
选项
A、GM crops could be environmentally beneficial and thus would be an essential tool for helping to feed the world’s burgeoning population.
B、GM crops cause too many concerns which would finally lead to restricting the planting of GM agricultural products.
C、The reassuring scientific findings bring more confidence in GM agricultural products.
D、As there are both supportive and negative findings of GM plants, the issue is till open to debate.
答案
D
解析
本文关于转基因作物这一具有争论性的话题做出的总结是什么?文章第六、第八段主题句点明转基因作物的优劣都难以界定,而文章结束也仅表示科学家会加紧研究,可见目前还没有得出明确的结论。
转载请注明原文地址:https://tihaiku.com/zcyy/3836274.html
相关试题推荐
Theworldseemsincreasinglydividedintothosewhofavorgeneticallymodifie
Theworldseemsincreasinglydividedintothosewhofavorgeneticallymodifie
Theworldseemsincreasinglydividedintothosewhofavorgeneticallymodifie
"LeftoverWomen"areincreasinglyvisibleintoday’sChina.Theyarethe
Individualsareincreasinglybeingaskedtotakeonsoleresponsibility—and
Individualsareincreasinglybeingaskedtotakeonsoleresponsibility—and
Individualsareincreasinglybeingaskedtotakeonsoleresponsibility—and
Individualsareincreasinglybeingaskedtotakeonsoleresponsibility—and
Individualsareincreasinglybeingaskedtotakeonsoleresponsibility—and
Individualsareincreasinglybeingaskedtotakeonsoleresponsibility—and
随机试题
ThedoctoradvisedthatMr.Malan()anoperationrightawaysoastosavehisli
关于水平布线的说法,不正确的有()A.水平布线的通道分为暗管预埋、墙面引线、
中间段照明与洞外亮度有关。()
导游人员为游客提供讲解服务的主要形式有( )。A.途中导游讲解 B.现场导游
收入中所占的比重一般在55%以上,在中国则不到42%,并呈现逐年下降的趋势,这给
A.蛛网膜下腔出血 B.短暂性脑缺血发作 C.脑栓塞 D.脑出血 E.脑
建安工程保险中,被保险人的索赔时效是()。A.自保险合同生效之日起,不超过2年
患者男性,37岁,素喜饮酒,日饮白酒2两,1月来脘腹不适,胃镜活检示:慢性萎缩性
关于预制混凝土楼梯工程量计量的说法,正确的是()。A.以立方米计量,按设计
发生应激性溃疡最常见的部位是( )。A.十二指肠 B.空肠 C.口腔 D
最新回复
(
0
)