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
At 5:30 in the morning we are deep in a dark forest on an island in the middle of the Panama Canal. We’ve been out walking for o
At 5:30 in the morning we are deep in a dark forest on an island in the middle of the Panama Canal. We’ve been out walking for o
admin
2011-01-02
38
问题
At 5:30 in the morning we are deep in a dark forest on an island in the middle of the Panama Canal. We’ve been out walking for only 15 minutes, but I’m already soaked in sweat.
As a colleague and I plod along, my head lamp picks out the occasional trail marker, but mainly the light seems to operate as a major local landmark for insects. Several mosquitoes have already discovered the delights of the soft parts of my ears, while others are slowly working their way between my socks and legs to be discovered later after much scratching. Suddenly a deranged roaring and barking starts 25m above my head and builds chaotically and intensity before slowly quieting after several minutes. Similar mad choruses respond from other areas of the forest. Hearing the dawn cacophony of howler monkeys always given me a deep sense of pleasure -- the joy of being back in the tropics. It may be a hot, humid place where insects, plants and fungi rule, but the phone and fax won’t find me here. I’m free to watch monkeys, collect data and try to tease out a tiny piece of the great puzzle of life’s diversity.
That diversity faces disaster, and every biologist has a horror story to tell. Each year many of us return to the field after a cold winter’s teaching to discover that-our research sites have been destroyed and our experiments and study organisms have disappeared. We can see with our own eyes the mass extermination of the world’s animal and plant life as forests, savannas and wetlands give way to farmland, housing developments and shopping malls. If current rates of habitat destruction continue, it is likely that we will condemn from a quarter to half the world’s currently living species to extinction within the next 100 years.
Nowhere is life more diverse than in tropical rain forests, and nowhere is the assault on life more tragic. Scientists are only beginning to understand the complex webs of interdependencies among various species. Increasingly, ecological research in the tropics in revealing how dependent humans are on forests for a wide variety of important services, particularly regulation of the earth’s atmosphere and climate. We may owe as much to the residents of the rain forests as we do our cattle, corn and wheat. Much of our understanding of tropical-forest biology comes from research on Barro Colorado Island, a 1,600-hectare dot in the middle of the Panama Canal. B.C.I. , as the island is affectionately known to the biologists who work there, is covered with dense tropical forest, which was declared a nature reserve in 1923. The Smithsonian Tropical Research Institute facility on B. C. I. , established in 1946, is a Mecca for tropical biologists, who work to uncover the complex links between the large variety of species that live in forests and to demonstrate the importance of these woodlands as sources for medicines and other products of incalculable value to humans.
The atmosphere at the research station is probably similar to that at Los Alamos, New Mexico, in the 1940s when a group of the world’s top physicists were cloistered together trying to design the atom bomb. The justified the creation of a nuclear weapon by assuming it would provide the ultimate deterrent that could be used to reinforce peace in a democratic world. Similarly, the longer-term future of human civilization on earth is dependent on the earth’s forests, which act as its lungs, livers and kidneys. That is why scientists on B. C. I. are struggling to unravel the mysteries of the forests before they disappear.
At first the forest in Panama just looks like a wall of green. Then you start to notice differences between plant species, and the sheer diversity seems suddenly overwhelming. Variations between plants are often subtle and only apparent for the short period of time that a species bears flowers or fruit. Slowly you begin to identify specific types and family groups such as the palms, heliconias and fig trees. Yet each of these families contains many species, every one of which has a subtle variation on an evolutionary theme that has found a slightly different way of competing for limited light and nutrients, or escaping from predators and diseases.
The fig trees provide a spectacular example of the complex interaction of species that enables forests to function. Of more than 1,000 species of figs in the world, at least 20 are found in Panama. Most tree species on B. C.I. bear fruit only seasonally, producing an abundance of it at the beginning of the rainy season in May and June. This is all consumed by variety of birds, monkeys and bats, and by the end of the rainy season, in October through December, there is a major shortage of food in the forest. Saving the day are the fig trees, which may bear fruit at any time.
Why do fig trees follow a different fruiting strategy from that of other trees? It turns out that figs are pollinated by tiny insects called fig wasps. The female wasp enters the fig flowers when they appear, lays her eggs and then dies. In the process she brings in fig pollen, which fertilizes the flower and spurs development of the fig fruit. Meanwhile the wasp’s eggs develop within the flower into larvae, which feed on some of the fruit before metamorphosing into adults and mating within the fruit. The males then die, while the females, by now covered in pollen, leave the fig in search of a new flower in which to lay their eggs, thus keeping the pollination going. Research by Allen Herre and colleagues at B. C.I. has shown that adult female fig wasps live for only two days and that each species of the fig wasp is specific to species of fig. Thus there always has to be a fig in flower while one is in fruit to ensure that the cycle continues. Since a fig-tree population must bear fruit all year because of the wasp’s short lifespan, the figs keep fruit-eating mammals alive during the fry season when other food sources are scarce. The fig tress are in turn dependent on these fruiteaters as dispersers of their seeds. Of course, the fruit-eaters also disperse the seeds of other plant species that produce fruit during the rainy season. This creates a long-term dependence of the other plants on the presence of figs.
All this suggests that a minimum number of fig trees is essential for a healthy tropical forest. Furthermore, studies from a variety of other habitats indicate that the disappearance of just one or two keystone species can lead to extinctions throughout the local community. In some cases it may take decades before trouble starts to show up.
Ultimately the forest has the vast potential of time to recover from almost anything we do to it. Like a large green heart, it has often expanded and contracted on a time scale of tens of thousands of years, while simultaneously fostering the diversity of species that inhabit the planet, including our own species. Unfortunately our human ability to understand our relationship to the forest and other habitats has to be mustered on a much faster time scale. Luckily scientists trying to demonstrate the dependence of humans on natural communities are making huge strides. History will show that their long-term contribution to the quality of life far exceeded those of other scientific endeavors such as the bombmaking at Los Alamos. It will also be far easier to justify their work to our grandchildren.
The author is primarily concerned with describing ______.
选项
A、research into tropical-forest biology on Barro Colorado Island
B、how the whole ecosystems can depend on the survival of a single species
C、the life cycle of the fig wasp
D、the importance of forests to the human race
答案
B
解析
该题问:作者主要是关注和描述什么?A项意为“对Barro Colorado岛的热带森林生物学的研究”,这在本文的第五段中有所提及,但并不是作者主要关心和描述的。B项意为“整个生态系统如何依靠单独一个种类的生存”。这是整个文章的中心,而且在本文的副标题中也清楚地显示此为文章的主旨“The demise of a single species can produce a cascade of extinctions and threaten an entire ecosystem”。C项意为“无花果黄蜂的生命循环”,这只是字面上的解释,不能反映出本文作者要说明的中心精神。D项意为“森林对人类的重要性”,这也不是作者要说明的。
转载请注明原文地址:https://kaotiyun.com/show/GplO777K
0
专业英语八级
相关试题推荐
Fromanearlyage,GraceMahoney’slifewasruledbyfear.Sherecallshavingherfirstpanicattackinnurseryschool,and"it
1 Whilethemissionofpublicschoolshasexpandedbeyondeducationtoincludesocialsupportandextra-curricularactivities,
Ofalltheareasoflearningthemostimportantisthedevelopmentofattitudes.Emotionalreactionsaswellaslogicalthought
Achildwhohasoncebeenpleasedwithatalelikes,asarule,tohaveitretoldinidenticallythesamewords,butthisshould
Professionalwomenwhoputcareersonholdforfamilyorotherreasonsearn18percentlessoncetheyreturntotheworkforce,a
IntheartoftheMiddleAges,weneverencounterthepersonalityoftheartistasanindividual;ratheritisdiffusedthrough
一切都是虚荣,人人皆爱虚荣,女人极其虚荣,男人也不甘落后——如果可能,他们则变本加厉。孩子也不例外,尤其是女孩子。其中一个正敲着我的腿,她想知道我对她的新鞋有何看法。坦白地说,这两只鞋并不怎么样,它们既不对称也没有曲线美,看上去有种无法形容的臃肿(同时我也
Mymother’shandsaredeepinCabbageleaves,hersleevespusheduppastherelbows,asshesiftsthroughwater,salt,andveget
近年来,由于就业问题日益严重,有些人建议让没有工作的未婚妇女来替换那些家务繁重的女工。有些当丈夫的还说:“让我们的爱人回家去,把她们的工资拿来贴补我们。我们从家务琐事中解放出来,工作就能干得更好。”有些有工作的母亲力图一面搞好家务,一面做好工作。她们也附和
Specialisationcanbeseenasaresponsetotheproblemofanincreasingaccumulationofscientificknowledge.Bysplittingupt
随机试题
变态反应可分几型?各型主要见于哪些皮肤疾病?
运营隧道的纵向通风方式有()。
()是指由同一公司所有,统一经营管理,具有统一的企业识别系统,实行集中采购和销售,由两个或两个以上连锁分店组成的一种形式。
某公司2010年主营业务收入30000元,主营业务成本15600元,营业税金及附加1230元.其他业务收入10000元,其他业务成本8700元,销售费、用8000元,管理费用5000元,财务费用一270元,营业外收支净额2340元。该公司营业利润为(
下列关于结算所和无负债结算制度的描述中,正确的有()。Ⅰ.结算所是期货交易的专门清算机构Ⅱ.逐日盯市制度能及时调整保证金账户,控制市场风险Ⅲ.结算所不以独立的公司形式组建Ⅳ.结算所实行无负债的每日结算制度,又被称为逐日盯市制度
某企业为大量大批的单步骤生产的企业,在计算产品成本时可采用的成本计算方法是()。
未来旅游活动的发展趋势将对导游服务产生直接影响并提出新的要求。新世纪导游服务的发展趋势是()
在教育目的问题上.法国教育家卢梭的主张体现了()。
(2010年国家.材料三)根据以下资料,回答下列问题。能够从上述资料中推出的是()。
设为正定矩阵,其中A,B分别为m阶,n阶对称矩阵,C为m×n矩阵。计算PTDP,其中
最新回复
(
0
)