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
During the last decade, Val Beasley of the University of Illinois College has led a team wanting to know why the world’s amphibi
During the last decade, Val Beasley of the University of Illinois College has led a team wanting to know why the world’s amphibi
admin
2012-06-10
44
问题
During the last decade, Val Beasley of the University of Illinois College has led a team wanting to know why the world’s amphibian(两栖动物) populations have been decreasing or riddled with deformed limbs.
Evidence from his and other teams points to increasing numbers of common parasites as an important cause. However, the problems facing amphibian habitats really pose a distressing example of ecosystems out of balance because of human activity, according to Beasley, a professor of biosciences and executive director of Wildlife and Ecosystem Health. Beasley’s main collaborators, postdoctoral researcher Anna M. Schotthoefer and Rebecca A. Cole, a scientist with the National Wildlife Health Center in Madison, Wis. , say they agree.
A series of their research projects -— two published in 2003 and another that will appear as a book chapter this year — dramatically refine the data on parasitic activity and argue that physically and chemically induced changes of aquatic habitats are taking a toll.
"We have to be asking what human activities are contributing to imbalances in these ecosystems to set the stage for more severe infections, " Beasley said. "It’s becoming a serious question of how we can better manage landscapes, streams, wetlands, ponds and lakes. Frogs are among the first animals that young children see in a healthy wild place, but they are not finding them in the same numbers as in past years. "
Tadpoles (蝌蚪) of many species feed on algae converting the material into the protein, fat and other nutrients that are needed by other creatures higher in the food chain, Beasley said. Amphibians are clearly important players in ecosystem functioning, he added. "The frogs that develop from tadpoles subsequently eat up thousands of insects," he said, "The frogs themselves are also important prey for reptiles, birds and mammals."
In the study funded by Chicago Zoological Society, Beasley’s team noted that Midwest landowners hollow out their ponds so that deep water prevents the establishment of aquatic plants.
Such a practice allows for easier boating, swimming and fishing, but by eliminating aquatic plants, the habitat becomes structurally barren. Herbicide use also aggravates the problem and produces chemical changes. Plant-derived oxygen is reduced, and herbicides also may have direct toxic effects on tadpoles and other animals, Beasley said. The lack of vegetation may expose tadpoles to more parasites coming from the infected snails, because the tadpoles can’t hide or use the vegetation to brush off the parasites, Schotthoefer said.
So while the parasites seem to contribute to declines and deformation in frog populations,the challenge is to find management approaches that put balance back into amphibian ecosystems, Beasley said.
The phrase "taking a toll" in the third paragraph probably means
选项
A、causing many deaths.
B、changing frogs’ behaviors.
C、accounting for human activities.
D、posing a threat to parasites.
答案
A
解析
第四段对第三段末句进行了解释:我们必须要问,哪些人类活动的后果导致这些生态系统的失衡,造成了两栖动物更加严重的感染…青蛙是孩子们在健康的野外环境中首先看到的动物之一,但现在,孩子们找不到像过去那么多的青蛙了。由物理因素和化学因素诱发水生栖息地发生变化的结果是“两栖动物更易感染疾病”。具体事例就是“青蛙数量的减少”,即青蛙大量死亡,故[A]为答案。
转载请注明原文地址:https://kaotiyun.com/show/jtmK777K
0
专业英语四级
相关试题推荐
SomehowCaliforniaisalwaysatthecuttingedge,beitintheflower-powerdaysofthe1960sorthedotcomboomofthe1990s.A
Accordingtothepassage,itisnoteasytogetseal
OfficialssaywaterlevelsalongtheBrahmaputraRiverstillareatdangerouslevelsalthough______.
Hetriedto______totheviewofthepublicmoredistinctlythaniscommonlydone.
Youhavebeenbadlyinjuredinacaraccident.Itisnecessarytogiveyouabloodtransfusionbecauseyoulostagreatdealof
There’samanatthereceptiondeskwhoseemsveryangryandIthinkhemeans______.trouble.
Didhegiveyouanything______theletter?
TheUnitedStatesiswell-knownforits【C1】______ofmajorhigherhighwaysdesignedtohelpa【C2】______getfromoneplaceto
TheUnitedStatesiswell-knownforits【C1】______ofmajorhigherhighwaysdesignedtohelpa【C2】______getfromoneplaceto
TheUnitedStatesiswell-knownforits【C1】______ofmajorhigherhighwaysdesignedtohelpa【C2】______getfromoneplaceto
随机试题
骨纤维管通过的是脊神经的
高级语言的翻译过程有两种形式,即编译和____________。
人体实验中应把什么放在首位
[1995年第027题]观演性建筑为了减小看台升起的坡度,而采取以下哪条措施是错误的?
商业银行的战略风险主要体现在()。
下列各项中,属于融资租赁优点的项。目有( )。
一位学生在班里丢了10元钱,班主任气不打一处来,让全班32名学生投票选“贼”,结果有2名学生入选。当2名学生要求拿出证据来,老师举起手中的选票:“这就是证据!”问题:班主任的做法对不对?为什么?
下列对于我国经济社会发展相关名词的解释,错误的是()。
Mt.DesertIslandThecoastoftheStateofMaineisoneofthemostirregularintheworld.Astraightlinerunningfromth
Individualsandbusinesseshavelegalprotectionforintellectualpropertytheycreateandown.Intellectualproperty【C1】______f
最新回复
(
0
)