首页
登录
职称英语
"Exotic and Endangered Species" When you hear someone bubbling enthusiastical
"Exotic and Endangered Species" When you hear someone bubbling enthusiastical
游客
2024-01-03
52
管理
问题
"Exotic and Endangered Species"
When you hear someone bubbling enthusiastically about an exotic species, you can safely bet the speaker isn’t an ecologist. This is a name for a resident of an established community that was deliberately or accidentally moved from its home range and became established elsewhere. Unlike most imports, which can’t take hold outside their home range, an exotic species permanently insinuates itself into a new community.
Sometimes the additions are harmless and even have beneficial effects. More often, they make native species endangered species, which by definition are extremely vulnerable to extinction. Of all species on the rare or endangered lists or that recently became extinct, close to 70 percent owe their precarious existence or demise to displacement by exotic species. Two examples are included here to illustrate the problem.
During the 1800s, British settlers in Australia just couldn’t bond with the koalas and kangaroos, so they started to import familiar animals from their homeland. In 1859, in what would be the start of a wholesale disaster, a northern Australian landowner imported and then released two dozen wild European rabbits (Oryctolagus cuniculus). Good food and good sport hunting—that was the idea. An ideal rabbit habitat with no natural predators was the reality.
Six years later, the landowner had killed 20,000 rabbits and was besieged by 20,000 more. The rabbits displaced livestock, even kangaroos. Now Australia has 200 to 300 million hippityhopping through the southern half of the country. They overgraze perennial grasses in good times and strip bark from shrubs and trees during droughts. You know where they’ve been; they transform grasslands and shrublands into eroded deserts. They have been shot and poisoned. Their warrens have been plowed under, fumigated, and dynamited. Even when all-out assaults reduced their population size by 70 percent, the rapidly reproducing imports made a comeback in less than a year. Did the construction of a 2,000-mile-long fence protect western Australia? No. Rabbits made it to the other side before workers finished the fence.
In 1951, government workers introduced a myxoma virus by way of mildly infected South American rabbits, its normal hosts. This virus causes myxomatosis. The disease has mild effects on South American rabbits that coevolved with the virus but nearly always had lethal effects on O. cuniculus. Biting insects, mainly mosquitoes and fleas, quickly transmit the virus from host to host. Having no coevolved defenses against the novel virus, the European rabbits died in droves. But, as you might expect, natural selection has since favored rapid growth of populations of O. cuniculus resistant to the virus.
In 1991, on an uninhabited island in Spencer Gulf, Australian researchers released a population of rabbits that they had injected with a calcivirus. The rabbits died quickly and relatively painlessly from blood clots in their lungs, hearts, and kidneys. In 1995, the test virus escaped from the island, possibly on insect vectors. It has been killing 80 to 95 percent of the adult rabbits in Australian regions. At this writing, researchers are now questioning whether the calcivirus should be used on a widespread scale, whether it can jump boundaries and infect animals other than rabbits (such as humans), and what the long-term consequences will be.
A vine called kudzu (Pueraria lobata) was deliberately imported from Japan to the United States, where it faces no serious threats from herbivores, pathogens, or competitor plants. In temperate parts of Asia, it is a well-behaved legume with a well-developed root system. It seemed like a good idea to use it to control erosion on hills and highway embankments in the southeastern United States. A With nothing to stop it, though, kudzu’s shoots grew a third of a meter per day. Vines now blanket streambanks, trees, telephone poles, houses, and almost everything else in their path. Attempts to dig up or burn kudzu are futile. Grazing goats and herbicides help, but goats eat other plants, too, and herbicides contaminate water supplies. B Kudzu could reach the Great Lakes by the year 2040.
On the bright side, a Japanese firm is constructing a kudzu farm and processing plant in Alabama. The idea is to export the starch to Asia, where the demand currently exceeds the supply. C Also, kudzu may eventually help reduce logging operations. D At the Georgia Institute of Technology, researchers report that kudzu might become an alternative source for paper. [br] The word exceeds in the passage is closest in meaning to
选项
A、surpasses
B、destroys
C、estimates
D、causes
答案
A
解析
In this passage, surpasses is a synonym for "exceeds." Context comes from the logical relationship between "demand" and "supply."
转载请注明原文地址:http://tihaiku.com/zcyy/3329568.html
相关试题推荐
"ExoticandEndangeredSpecies"→Whenyouhearsomeonebub
"ExoticandEndangeredSpecies"→Whenyouhearsomeonebub
"ExoticandEndangeredSpecies"→Whenyouhearsomeonebub
"ExoticandEndangeredSpecies"→Whenyouhearsomeonebub
"ExoticandEndangeredSpecies"→Whenyouhearsomeonebub
"ExoticandEndangeredSpecies"→Whenyouhearsomeonebub
"ExoticandEndangeredSpecies"→Whenyouhearsomeonebub
[audioFiles]audio_etoefz_013(20051)[/audioFiles]A、Shemightknowsomeonewhone
Ecologistshavestudiedthefourchipmunkspeciesthatoccurontheeastern
Themostaggressiveofthefoureastern-slopespeciesisthelodgepolechipm
随机试题
Choosethecorrectletter,A,BorC.CourseFeedback[br]A
Ofthefollowinglinguists,______belongstoLondonSchool.A、BoasB、SapirC、Bloo
[originaltext]BetweentenandmidnighttheUnitedStatesispoliticallylea
"可使血管扩张充血,促进血液循环,增强新陈代谢,使神经兴奋性降低"的是A.温水浴
已知“预付账款”账户本期借方发生额为5400元,贷方发生额为3000元,期末借方
当代大学生应当树立正确的择业观。下列表述体现正确的择业观的有A.职业活动不仅是人
地西泮临床应用为首选用于()A.癫痫大发作 B.抑郁症 C.精神病 D.慢
有关慢性支气管炎的诊断标准,咳嗽、咳痰反复发作时间应为A.每年发作至少3个月,持
根据《最高人民法院关于审理建设工程施工合同纠纷案件适用法律问题的解释》,下列情形
因不可抗力解除合同的,发包人不应向承包人支付的费用是( )。A.合同解除前承包人
最新回复
(
0
)