PP-T2-ESSAY2

[Huang Hsin-Yi]

Essay #2. 091 (21422-!-item-!-188;#058&00091-00)

More selective than most chemical pesticides in that they ordinarily destroy only unwanted species, biocontrol agents (such as insects, fungi, and viruses) eat, infect, or parasitize targeted plant or animal pests. However, biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources: a biocontrol agent might reduce the benefits conferred by a desirable animal species by consuming a plant on which the animal prefers to lay its eggs. Another example of indirect negative consequences occurred in England when a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring. The paucity of known extinctions or disruptions resulting from indirect interactions may reflect not the infrequency of such mishaps but rather the failure to look for or to detect them: most organisms likely to be adversely affected by indirect interactions are of little or no known commercial value and the events linking a biocontrol agent with an adverse effect are often unclear. Moreover, determining the potential risks of biocontrol agents before they are used is difficult, especially when a nonnative agent is introduced, because, unlike a chemical pesticide, a biocontrol agent may adapt in unpredictable ways so that it can feed on or otherwise harm new hosts.

Question #5. 091-0(21468-!-item-!-188;#058&000091-01)

The passage is primarily concerned with

(A) explaining why until recently scientists failed to recognize the risks presented by biocontrol agents
(B) emphasizing that biocontrol agents and chemical pesticides have more similarities than differences
(C) suggesting that only certain biocontrol agents should be used to control plant or animal pests
(D) arguing that biocontrol agents involve risks, some of which may not be readily discerned
(E) suggesting that mishaps involving biocontrol agents are relatively commonplace

Ans:D

Question #6. 091-03(21514-!-item-!-188;#058&000091-03)

According to the passage, which of the following is a concern that arises with biocontrol agents but not with chemical pesticides?

(A) Biocontrol agents are likely to destroy desirable species as well as undesirable ones.
(B) Biocontrol agents are likely to have indirect as well as direct adverse effects on nontarget species.
(C) Biocontrol agents may change in unforeseen ways and thus be able to damage new hosts.
(D) Biocontrol agents may be ineffective in destroying targeted species.
(E) Biocontrol agents may be effective for only a short period of time.

Ans:C
可以理解C的正確答案,卻不知如何排除B ;-S


Question #7. 091-06(21560-!-item-!-188;#058&000091-06)

The passage suggests which of the following about the blue butterfly mentioned in the highlighted text?

(A) The blue butterfly's survival was indirectly dependent on sustaining a rabbit population of a particular size.
(B) The blue butterfly's survival was indirectly dependent on sustaining large amounts of vegetation in its habitat.
(C) The blue butterfly's survival was threatened when the ants began preying on its offspring.
(D) The blue butterfly was infected by the virus that had been intended to control rabbit populations.
(E) The blue butterfly was adversely affected by a biocontrol agent that competed with it for resources.

Ans:A

[Huang Hsin-Yi]

More selective than most chemical pesticides in that they ordinarily destroy only unwanted species, biocontrol agents (such as insects, fungi, and viruses) eat, infect, or parasitize targeted plant or animal pests. However, biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources: a biocontrol agent might reduce the benefits conferred by a desirable animal species by consuming a plant on which the animal prefers to lay its eggs. Another example of indirect negative consequences occurred in England when a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring. The paucity of known extinctions or disruptions resulting from indirect interactions may reflect not the infrequency of such mishaps but rather the failure to look for or to detect them: most organisms likely to be adversely affected by indirect interactions are of little or no known commercial value and the events linking a biocontrol agent with an adverse effect are often unclear. Moreover, determining the potential risks of biocontrol agents before they are used is difficult, especially when a nonnative agent is introduced, because, unlike a chemical pesticide, a biocontrol agent may adapt in unpredictable ways so that it can feed on or otherwise harm new hosts.

我想從這段話,可推出chemical pesticides 和biocontrol agents 都會對nontarget species 有負面影響,只是程度不同,方法不同,
所以Q6-B不行

[amazingslim]

這篇是GWD24-3~6
http://www.formosamba.com/phpBB3/viewtopic.php?t=3656
可以參考ㄧ下

[Huang Hsin-Yi]

謝謝,看來我的題目沒吃透

[purpleme]

Question #7. 091-06(21560-!-item-!-188;#058&000091-06)

The passage suggests which of the following about the blue butterfly mentioned in the highlighted text?

(A) The blue butterfly's survival was indirectly dependent on sustaining a rabbit population of a particular size.
(B) The blue butterfly's survival was indirectly dependent on sustaining large amounts of vegetation in its habitat.
(C) The blue butterfly's survival was threatened when the ants began preying on its offspring.
(D) The blue butterfly was infected by the virus that had been intended to control rabbit populations.
(E) The blue butterfly was adversely affected by a biocontrol agent that competed with it for resources.

Ans:A

請問這題答案D為什麼不行呢?
是因為by the virus嗎?

[cfmolly]

Question #7. 091-06(21560-!-item-!-188;#058&000091-06)

The passage suggests which of the following about the blue butterfly mentioned in the highlighted text?

(A) The blue butterfly's survival was indirectly dependent on sustaining a rabbit population of a particular size.
(B) The blue butterfly's survival was indirectly dependent on sustaining large amounts of vegetation in its habitat.
(C) The blue butterfly's survival was threatened when the ants began preying on its offspring.
(D) The blue butterfly was infected by the virus that had been intended to control rabbit populations.
(E) The blue butterfly was adversely affected by a biocontrol agent that competed with it for resources.

Ans:A

我想請問一下為什麼E不行!?
回到文章當中找到Another example的位置
往上就可以推得這個例子是在解釋
biocontrol agents can negatively affect nontarget species by competing with them for resources.

誰來幫我解答一下
感激不盡!!!