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
A、Only a few of them cause problems to native species. B、They may turn out to benefit the local environment. C、Few of them can s
A、Only a few of them cause problems to native species. B、They may turn out to benefit the local environment. C、Few of them can s
admin
2019-03-08
52
问题
Governments, private groups and individuals spend billions of dollars a year trying to root out non-native organisms that are considered dangerous to ecosystems and to prevent the introduction of new intruders. [16] But a number of scientists question the assumption that the presence of alien species can never be acceptable in the natural ecosystem. They say that portraying introduced species as inherently bad is an unscientific approach. [17] “Distinctions between exotic and native species are artificial,” said Dr.Michael Rosensberg, a professor of evolutionary biology at the University of Arizona. Because they depend on picking a date and calling the plants and animals that show up after that date exotic. “Ecosystem’s free of species to find as exotic are by default considered the most natural. You can’t roll back the clock and remove all exotics or fix habitats,” Dr.Rosensberg said. Both native and exotic species can become invasive and so they all have to be monitored and controlled when they begin to get out of hand. At its core, the debate is about how to manage the world’s remaining natural ecosystems and about how and how much to restore other habitats. Species that invade a territory can harm ecosystems, agriculture and human health. They can threaten some native species or even destroy and replace others. “Next to habitat loss, these invasive species represent the greatest threat to biodiversity worldwide,” many ecologists say. Ecologists generally define an alien species as one that people accidentally or deliberately carried to its new location. Across the American continents, exotic species are those introduced after the first European contact. That date rounded up to 1500 AD represents what ecologists consider to have been in major shift in the spread of species including crops and livestock, as they begin to migrate with humans from continent to continent. [18] “Only a small percentage of alien species cause problems in their new habitats,” said Don Smith, professor of ecology and evolutionary biology at the University of Tenacy. “Of the 7,000 alien species in the United States, out of a total of 150,000 species, only about 10% are invasive,” he pointed out. The other 90% have fit into their environment and are considered naturalized. Yet appearances can deceive, ecologists caution, and many of these exotics may be considered acceptable only because no one has documented their harmful effects. What is more, non-native species can appear harmless for decades then turn invasive.
Questions 16 to 18 are based on the recording you have just heard.
16.What assumption about introduced species is challenged by a number of scientists?
17.What does Dr.Michael Rosensberg think of the exotic and native species?
18.What does Professor Don Smith say about alien species?
选项
A、Only a few of them cause problems to native species.
B、They may turn out to benefit the local environment.
C、Few of them can survive in their new habitats.
D、Only 10 percent of them can be naturalized.
答案
A
解析
浏览四个选项,根据选项中出现的cause problems to native species,benefit the local environment,survive,naturalized等词可以推测,该题可能和外来物种有关。题干问的是唐·史密斯教授提到关于外来物种的什么内容。讲座中提及,生态学和进化生物学教授唐·史密斯认为,只有少量的外来物种会给它们的新栖息地造成问题,故答案为A(它们之中只有少量物种会对本土物种造成问题)。B项(它们可能会对当地环境有益处)在文中并未提及,故排除。C项(它们之中只有很少一部分能在新栖息地生存下去)和D项(只有10%的物种能被驯化)不符合讲座内容,故排除。
转载请注明原文地址:https://kaotiyun.com/show/faH7777K
0
大学英语六级
相关试题推荐
Spidersareknownformanythings.Sociabilityisnotoneofthem.Mostspidersaremorelikelytotrytoeattheirneighbourst
DeerPopulationsofthePugetSoundA)TwospeciesofdeerhavebeenprevalentinthePugetSoundareaofWashingtonStateinth
WhyCan’tAmericanStudentsCompete?TwiceasmanystudentsinSingaporeareproficientinmathasintheUnitedStates.
CheatinginGCSEandA-Levelsbypupils,teachersandevenschoolexamcentresrosemarkedlylastyear,withevermoresophistic
Children’sHealthcareofAtlantawantstomoveGeorgiaoutofthetop10listforchildhoodobesity(肥胖)by2016,officialssaid.
A、Herwell-preparedspeech.B、Hermotivationandinterest.C、Heruniquemusicbackground.D、Hergoodexplanations.C男士说他认为女士的音乐背
Depression[A]Inbed,youtossandturn,unabletogetagoodnight’ssleep.Youfeelanxiousandworried.There’splentytod
A、Rememberingworddefinitions.B、Recognizingrepeatednumbers.C、Distinguishingbetweensimilarcolors.D、Tastingsounds.D细节题。
Throughoutevolution,humanshavebeenactive.Ourancestorschasedpreyashunter-gatherersand【C1】______frompredators.Morer
随机试题
被动转运(passivetransport)
根据以下材料,回答问题。①几百万年前,气候变化导致森林退化,人类祖先被迫走出森林,到草原上生活。这被认为是人类与其生活在森林里的类人猿亲戚们分化的关键时刻。传统观点认为,在草原上,猿人们很快过上了狩猎者的生活。作为灵长类生物,他们并不具备强健的肌肉和锋利
植物新品种可以通过______方式获得植物新品种权。()
建筑物中结构构件的安全等级不得低于()级。
甲油田是增值税一般纳税人,以1个月为1个纳税期缴纳增值税和资源税,2018年6月发生以下业务:(1)开采原油45万吨,伴采天然气2100万立方米。(2)当月开采原油过程中用于加热使用自采原油5万吨,其余40万吨原油当月全部销售,取得不舍增值税销售额38
2014年,第十二届全国人民代表大会常务委员会第十次会议将()设立为烈士纪念日。
战略数据规划方法认为,实体分析是自顶向下确定企业实体的过程,而经验证明,实体分析过程需安排【】处理的高级管理人员参加。
对考生目录下的数据库“hospital”建立文件名为“bd3”的表单。表单含有一个表格控件,用于显示用户查询的信息;表单上有一个按钮选项组,含有“药品查询”“处方查询”和“综合查询”3个选项按钮;表单上有两个命令按钮,标题分别为“查询”和“关闭”。
Onthebalancesheet,assetsandliabilitiesareclassifiedaseither(61)orlong-termtoindicatetheirrelativeliquidity.
TheInternetisagiantnetworkofcomputerslocatedal]overtheworldthatcommunicatewitheachother.TheInternetisan
最新回复
(
0
)