One RC question needs clarification

[yvonne_mo]

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.



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.

I originally got A for this one, but the answer is C. Can some one please explain to me why A is wrong? I read some of the posts, people are saying because the first sentence indicates A is wrong, it means for most chemical pesticides, not biocontrol agents. Can anyone explain to me if that is right? When the sentence construct as:
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.
What they refers to in this particular sentence, is it refers to pesticides or agents? I thought C is right because the sentence:
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.

Can someone please also explain to me what does it mean "reduce the benefits conferred by a desirable animal species"

Thank you!

[RonPurewal]

what is the source of this question?


this question is explictly answered in the last sentence of the passage: unlike a chemical pesticide, a biocontrol agent may adapt in unpredictable ways so that it can feed on or otherwise harm new hosts.

[bolopaneer]

[RonPurewal]

bolopaneer, thanks.

I originally got A for this one, but the answer is C. Can some one please explain to me why A is wrong?

the first sentence of the passage is the direct opposite of (a).
that sentence says that biocontrol agents are "more selective than chemical pesticides in that they typically only destroy unwanted species".
"in that" is a phrase used when we are giving the specific way in which something is true. therefore, the sentence says that biocontrol agents typically just target the unwanted species -- and this makes them "more selective than chemical pesticides". if that's true, then chemical pesticides must also destroy some species that are NOT unwanted.

this answer choice is therefore the opposite of what we want here.

What they refers to in this particular sentence, is it refers to pesticides or agents?

that whole group of words is a modifier of "biocontrol agents", so it can be inferred that the given description is a description of biocontrol agents.

Can someone please also explain to me what does it mean "reduce the benefits conferred by a desirable animal species"

this means that some other animal species has positive effects (benefits) in some situation; "reduce the benefits" signifies that the use of biocontrol agents will work against those positive effects.

[martelena]

This is another question from GMAT Prep (test 2) related to the same passage.

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

Official answer: [D]

Can somebody explain why the correct answer is better than choice A and what's wrong with A?

[tim]

well, the correct answer is better because A is wrong. :) why is A wrong? this is the type of question you should anticipate before it shows up, so you should already have an idea in mind of what the passage is about. without looking at the answer choices, you should recognize that this passage is about SOMETHING having to do with biocontrol agents. in particular, the passage is about the risks posed by biocontrol agents. the problem with A is it incorrectly puts the focus on the scientists and whether they recognized the risks. this is only a small part of the passage, and certainly not the primary focus..

[jp.jprasanna]

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

Hi Tim Could you please let me know why is E wrong for the above question. Is it because it only talk abt a small portion of the passage. I was referring to the below section from the passage...

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:

[tim]

yep, same deal as with my other post. just because something is mentioned in the passage doesn't automatically make the passage's primary focus..

[chetan86]

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 consequcnces 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.


4. The example presented by the author in highlight text most clearly serves to illustrate
A. a situation in which a species is less vulnerable to biocontrol agents than it would have been to chemical pesticides.
B. a way in which the introduction of a biocontrol agent can affect a non target species.
C. a nonnative agent's adapting in an unpredictable way that results in damage to a new host.
D. The contention that biocontrol agents can harm non target species by competing with them for resources
E. the way in which indirect consequences from the use of biocontrol agents are most likely to occurs.

OA : B
Could you please explain why D is wrong?
D is wrong because of the word 'contention'?

The highlighted information is related to the sentence : biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources

Thanks!!
Chetan

[jnelson0612]

D talks about competing for resources, and this is what makes it wrong.

Read your highlighted portion again:
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.

If you read this through, it wasn't that the various species "competed" for resources. It was just that the virus reduced the rabbits, which affected the ground cover, which reduced the aunt nests, and then finally a butterfly became extinct because it had depended on those nests to shelter its offspring.

If it were a case of competing for resources, I would expect it to say something like there wasn't enough water, food, or other necessary substances for all the species. This does not indicate that, and rather, just shows the interconnectedness of the species and how something that effects one can have a resulting effect on another.

[RonPurewal]

incidentally, it's possible to eliminate choice (d) even if you don't understand the specifics at all.

just note the transitions:

(paragraph 1)
biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources: ...

(paragraph 2)
Another example of indirect negative consequences...

the thing in paragraph 2 is "another" example—i.e., they're explicitly telling you that it's NOT a continuation of the first example.

[chetan86]

incidentally, it's possible to eliminate choice (d) even if you don't understand the specifics at all.

just note the transitions:

(paragraph 1)
biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources: ...

(paragraph 2)
Another example of indirect negative consequences...

the thing in paragraph 2 is "another" example—i.e., they're explicitly telling you that it's NOT a continuation of the first example.

Hi Jamie/Ron,

Thanks a lot for your reply.
Now I understood my mistake. I thought second example is continuation of first example. :(
I am required to read more actively!!

Thanks!!
Chetan

[RonPurewal]

yep.

[tim]

Let us know if there are any further questions on this one.

[liu1993918]

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

The OA is E.
However, I choose A. Since the 1st sentence of the passage--More selective than most chemical pesticides in that they ordinarily destroy only unwanted species, biocontrol agents eat, infect, or parasitize targeted plant or animal pests.-- told me a difference between chemical pesticides and biocontrol agents.
Can instructors told me why A is wrong, please?

Furthermore, I have another question, which is more important.
I know that the last sentnce of the passage answers the above question. However, I didn't read the last sentence when I was dealing with this passage. I just skim very quickly after I read this sentence: "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“. This sentence told me that the content below centers on the issue of failture to detect mishaps, so it is very difficult for me to notice this sentence.
Thus, I am confused. How can I read the whole passage very quickly and meanwhile notice some sentence like the last sentence in this passage? Thanks in advance.