Reading Comprehension

[Reading Comprehension] 试题详情

    A small number of the forest species of lepidoptera (moths and butterflies, which exist as caterpillars during most of their life cycle) exhibit regularly recurring patterns of population growth and decline-such fluctuations in population are known as population cycles. Although many different variables influence population levels, a regular pattern such as a population cycle seems to imply a dominant, driving force. Identification of that driving force, however, has proved surprisingly elusive despite considerable research. The common approach of studying causes of population cycles by measuring the mortality caused by different agents, such as predatory birds or parasites, has been unproductive in the case of lepidoptera. Moreover, population ecologists' attempts to alter cycles by changing the caterpillars' habitat and by reducing caterpillar populations have not succeeded. In short, the evidence implies that these insect populations, if not self-regulating, may at least be regulated by an agent more intimately connected with the insect than are predatory birds or parasites.

    Recent work suggests that this agent may be a virus. For many years, viral disease had been reported in declining populations of caterpillars, but population ecologists had usually considered viral disease to have contributed to the decline once it was underway rather than to have initiated it. The recent work has been made possible by new techniques of molecular biology that allow viral DNA to be detected at low concentrations in the environment. Nuclear polyhedrosis viruses are hypothesized to be the driving force behind population cycles in lepidoptera in part because the viruses themselves follow an infectious cycle in which, if protected from direct sun light, they may remain virulent for many years in the environment, embedded in durable crystals of polyhedrin protein. Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect's cells. Late in the course of the infection, millions of new virus particles are formed and enclosed in polyhedrin crystals. These crystals reenter the environment after the insect dies and decomposes, thus becoming available to infect other caterpillars. One of the attractions of this hypothesis is its broad applicability. Remarkably, despite significant differences in habitat and behavior, many species of lepidoptera have population cycles of similar length, between eight and eleven years. Nuclear polyhedrosis viral infection is one factor these disparate species share.
The primary purpose of the passage is to

Options:

describe the development of new techniques that may help to determine the driving force behind population cycles in lepidoptera
present evidence that refutes a particular theory about the driving force behind population cycles in lepidoptera
present a hypothesis about the driving force behind population cycles in lepidoptera
describe the fluctuating patterns of population cycles in lepidoptera
question the idea that a single driving force is behind population cycles in lepidoptera

Correct:

C

Reading Comprehension

0评分
82浏览

[点此查看答疑][GWD]Reading Comprehension

我完全读不出这是提出了一个假设,就读出第一段讲了个传统方法研究那个lepidoptear的population cycles什么的,第二段又说了最近的work解释了个agent怎么样,所以就选了A,其实此题毫无思路,请求老师指点
0评分
71浏览

[点此查看答疑][GWD]Reading Comprehension

想问下老师,这种问primary purpose是怎么做的,我选的是D,这个D我是根据前面判断的,我觉得C那个hypothesis仅仅是随着一些东西的发现后面推出来的,可是没有前面就没有后面呀,是不是问这种primary purpose的题目是根据最终的一个观点或现象来做判断还是根据文章大部分的段落句子在讨论的东西做出判断,如果是比如这篇文章改下,后面也是提出hypothesis,不过只是几句话带过,也否定了前面的东西,修饰的语句少了,是不是就不能选这个选项了?
0评分
82浏览

[点此查看答疑][GWD]Reading Comprehension

我完全读不出这是提出了一个假设,就读出第一段讲了个传统方法研究那个lepidoptear的population cycles什么的,第二段又说了最近的work解释了个agent怎么样,所以就选了A,其实此题毫无思路,请求老师指点
0评分
71浏览

[点此查看答疑][GWD]Reading Comprehension

想问下老师,这种问primary purpose是怎么做的,我选的是D,这个D我是根据前面判断的,我觉得C那个hypothesis仅仅是随着一些东西的发现后面推出来的,可是没有前面就没有后面呀,是不是问这种primary purpose的题目是根据最终的一个观点或现象来做判断还是根据文章大部分的段落句子在讨论的东西做出判断,如果是比如这篇文章改下,后面也是提出hypothesis,不过只是几句话带过,也否定了前面的东西,修饰的语句少了,是不是就不能选这个选项了?

问个问题

点我领取
免费专项课程
在线咨询