首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The world seems increasingly divided into those who favor genetically modified (GM) foods and those who fear them. Advocates ass
The world seems increasingly divided into those who favor genetically modified (GM) foods and those who fear them. Advocates ass
admin
2019-11-02
51
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?
What is the focus of the debate concerning GM crops?
选项
A、Whether it is environmental-friendly.
B、Whether it is healthy to people.
C、Whether it will cause influences on surrounding lives.
D、Whether it is safe.
答案
D
解析
关于转基因作物的争论焦点在于什么?文章第一段就介绍了关于转基因作物的不同观点,涉及环境、人体健康等,但有明确信息指出“主要的争议,集中在基因改造食物的安全性上”,故答案为D。
转载请注明原文地址:https://kaotiyun.com/show/FkbK777K
0
专业英语八级
相关试题推荐
Somesocialscientistshaveclaimedthatdivorceharmschildrenfortherestoftheirlivesleadingthemtoformmarriagesash
It’stheholidayseasonandthatmeanskidsbythemillionsareaskingSantafortheopportunitytoblowawayenemysoldiersan
Educationalphilosophyhaschangedagreatdealinthe50yearssinceIwasinschool.Backthen,forexample,Ihadthehighe
EvelynCokespent20yearsasahomecareaidehelpingtheelderlyandthesick,butshedidnotliveandseefairlaborlaws【M1
Theagingprocessisnotentirelydeterminedbyheredity,butisinfluencedbydifferentenvironmentalandsocialcircumstances
GeneralIdeasaboutRhetoricI.Thedefinition&understandingofrhetoricA.Dictionarydefinition:theartofusingwords【T1】
Theveryfirsttopicofourdiscussionis"whatisart?"Mytalktodaywillbedividedintotwoparts.Inthefirstpartofmyt
Individualsareincreasinglybeingaskedtotakeonsoleresponsibility—andassumetheburdenofrisk—forcomplexsavingstasks
人生有三重境界,这三重境界可以用一段充满禅机的语言来说明,这段语言便是:看山是山,看水是水;看山不是山,看水不是水;看山还是山,看水还是水。这就是说一个人的人生之初纯洁无瑕,初识世界,一切都是新鲜的,眼睛看见什么就是什么,人家告诉他这是山,他就认识了山,
随机试题
一年轻男性,在建筑工地不慎摔下,背部着地,送至医院时四肢运动不能,呼吸浅快,拟行急诊椎管减压内固定手术。该病人禁忌使用的肌松药为
容易转变为急性心肌梗死的疾病包括
枳实消痞丸与半夏泻心汤共有的药物是
超声探头频率的临床应用,下列哪项是错误的
A.血瘀型B.气虚型C.肾虚型D.产伤型E.脾虚型产后小便不通,小腹胀满刺痛,乍寒乍热,舌暗,苔薄白,脉沉涩。其中医证型是
甲乙两人是某大学学生,甲经常通过校园网出售一些二手东西。一日,两人通过MSN洽谈二手掌上电脑的买卖事宜。甲称:“我有掌上电脑一台,配置为……,九成新,附有数码照片可供参考,2800元要不要?"乙回话称:“东西不错,2400元的话可以接受。”甲回复:“可以,
2006年3月10日,王某因“殴打他人”被县公安局传唤24小时后处以10日拘留,因王某为外地人找不到保人且经济拮据交不起保证金被立即送达拘留所执行,王某提出听证的请求也被拒绝。王某于3月20日(传唤一日折抵拘留一日)释放后向市公安局申请复议,复议机关维持了
土的干密度越大,土越密实。()
下列关于确定最佳现金持有量的随机模式和存货模式的表述中,正确的有()。
若窗体上有一个名为Command1的命令按钮,并有下面的程序:PrivateSubCommand1_Click() Dimarr(5)AsInteger Fork=1To5 arr(k)=k Nextk prog
最新回复
(
0
)