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GraceSCKao
Joined: 02 Jul 2021
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10 Dec 2021, 21:12
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GMATNinja
Question 2
GraceSCKao
Hi GMATNinja,
I have read all the previous posts but am still a bit unsure about the second question.
I got the option (D) by mapping and eliminating all other options, but the wording in the option (D) seems problematic to me. I know that a change of even one single word can greatly change the reasoning in GMAT, so I would like to know whether my doubt makes sense.
The passage clearly says that "Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear," so I know that the failure of some salmon to return to their home streams provides a way by which another streams can be repopulated, if the fish there disappear.
But, the condition in the option (D) is "should the stream recover," which the passage does not mention clearly.
I know that previously a few members or experts, while analyzing this condition, made inferences that the stream should have be restored first so that the new fish that stray and arrive in the stream can survive there.
But, after reading many RC passages regarding biology, I find it hard to believe that such inference could be made with complete certainty. The disappearance of the first group of fish could be attributed to many reasons other than environmental damage, such as an increase in its predators. In this case, the condition in the option (D) "should the stream recover" seems out of place.
Even if we assume that the first group of fish disappeared due to environmental damage, there is still a chance that the second group of fish can survive in the damaged waters, even though the stream has not recovered, as different species of animals have different tolerance for environmental pollution (I presume that this is is a common sense.) In this case, the condition in the option (D) "should the stream recover" seems also out of place.
The second question is an inference question, so we need to find an answer whose information is implied by the passage. I just do not think the condition "should the stream recover" works here.
Hope you can clarify my doubt if you are available. Thank you very much.
VRC000460-02
2. It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which
(A) pristine streams that are near polluted streams become polluted themselves
(B) the particular adaptations of a polluted stream’s salmon population can be preserved without dilution
(C) the number of salmon in pristine habitats decreases relative to the number in polluted streams
(D) an environmentally degraded stream could be recolonized by new salmon populations should the stream recover
(E) the extinction of the salmon populations that spawn in polluted streams is accelerated
You're right that this is an inference question -- in other words, the correct answer choice will NOT be stated directly in the passage. So, you can't use the fact that (D) isn't directly stated in the passage to eliminate (D).I have read all the previous posts but am still a bit unsure about the second question.
I got the option (D) by mapping and eliminating all other options, but the wording in the option (D) seems problematic to me. I know that a change of even one single word can greatly change the reasoning in GMAT, so I would like to know whether my doubt makes sense.
The passage clearly says that "Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear," so I know that the failure of some salmon to return to their home streams provides a way by which another streams can be repopulated, if the fish there disappear.
But, the condition in the option (D) is "should the stream recover," which the passage does not mention clearly.
I know that previously a few members or experts, while analyzing this condition, made inferences that the stream should have be restored first so that the new fish that stray and arrive in the stream can survive there.
But, after reading many RC passages regarding biology, I find it hard to believe that such inference could be made with complete certainty. The disappearance of the first group of fish could be attributed to many reasons other than environmental damage, such as an increase in its predators. In this case, the condition in the option (D) "should the stream recover" seems out of place.
Even if we assume that the first group of fish disappeared due to environmental damage, there is still a chance that the second group of fish can survive in the damaged waters, even though the stream has not recovered, as different species of animals have different tolerance for environmental pollution (I presume that this is is a common sense.) In this case, the condition in the option (D) "should the stream recover" seems also out of place.
The second question is an inference question, so we need to find an answer whose information is implied by the passage. I just do not think the condition "should the stream recover" works here.
Hope you can clarify my doubt if you are available. Thank you very much.
VRC000460-02
2. It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which
(A) pristine streams that are near polluted streams become polluted themselves
(B) the particular adaptations of a polluted stream’s salmon population can be preserved without dilution
(C) the number of salmon in pristine habitats decreases relative to the number in polluted streams
(D) an environmentally degraded stream could be recolonized by new salmon populations should the stream recover
(E) the extinction of the salmon populations that spawn in polluted streams is accelerated
Think about the role of the words "should the stream recover." Here, they LIMIT the circumstances in which an environmentally degraded stream could be repopulated by straying.
The passage tells that low levels of straying mean that a "location can be repopulated should the fish there disappear." There are no limitations placed on why the fish disappeared in the first place, or what happened to the environment after that.
From this, you could make all kinds of inferences -- for example, if the fish disappeared because of over-fishing, then you could infer that straying would allow the location to be repopulated once fishing is limited again in the area.
Equally, you could infer that if the fish disappeared because of environmental degradation, then straying would allow the location to be repopulated once the environment recovers. This is what (D) tells us. Sure, it's just one circumstance out of many possible circumstances. But that limitation is totally fine -- we can still infer (D), so that's the correct answer to question 2.
I hope that helps!
Thank you so much!!! It definitely helps!
It seems that I confused the two concepts: inference and stated meaning.
Thank you sir for your elaboration on inference; now I see it better!
16 Nov 2022, 23:06
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KarishmaB
2. It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which
(A) pristine streams that are near polluted streams become polluted themselves
(B) the particular adaptations of a polluted stream’s salmon population can be preserved without dilution
(C) the number of salmon in pristine habitats decreases relative to the number in polluted streams
(D) an environmentally degraded stream could be recolonized by new salmon populations should the stream recover
(E) the extinction of the salmon populations that spawn in polluted streams is accelerated
@KarishmaB explanation:
The passage says: Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear.
This sentence means that straying is crucial because it provides a mechanism by which the current location can be repopulated (it is already populated so it can be repopulated) should the fish here disappear.
Say today some fish stray to other streams. Say after 1 month, the condition of this stream deteriorates such that all the fish in it die. After a few months, this stream is cleaned up and its waters can support life again. Then the fish that had strayed can be brought back here to repopulate these waters.[/quote]
Passage tells us: Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted.
So some fish from stream A stray to stream B. Now stream B fish have some local adaptations. If too many fish from stream A come to stream B, those local adaptations could be lost. This could result in lower the overall fitness of subsequent generations."
GMATNINJA explanation:
[b]GMATNinja[/b]
"Think about the role of the words "should the stream recover." Here, they LIMIT the circumstances in which an environmentally degraded stream could be repopulated by straying.
The passage tells that low levels of straying mean that a "location can be repopulated should the fish there disappear." There are no limitations placed on why the fish disappeared in the first place, or what happened to the environment after that.
From this, you could make all kinds of inferences -- for example, if the fish disappeared because of over-fishing, then you could infer that straying would allow the location to be repopulated once fishing is limited again in the area.
Equally, you could infer that if the fish disappeared because of environmental degradation, then straying would allow the location to be repopulated once the environment recovers. This is what (D) tells us. Sure, it's just one circumstance out of many possible circumstances. But that limitation is totally fine -- we can still infer (D), so that's the correct answer to question 2."
Hello GMATNinja and @KrishmaB
From your explanations for the meaning of "Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear. Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted.", I understand as follows:
- A location (or environment/ stream/ habitat) had degraded because of some event (for example environmental degradation), so the fish in this location disappeared. But then this location recovered.
- Next, a low rate of new salmon fish stray to this location (instead of returning their natal stream because of this stream was degraded). Because of LOW RATE, this location is recolonized/ repopulated.
I am confused: If the fish in this location disappeared, there is no fish. Therefore, the new salmon fish do not interbreed with any existing fish. (interbreed with whom?) Therefore, low rate or high rate of straying does not matter with dillution in this location. In other words, any rate of straying can help this location to be recolonized.
Please help me to clear my mind.
Thank you very much
16 Nov 2022, 23:29
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TrungTiger
KarishmaB
2. It can be inferred from the passage that the occasional failure of some salmon to return to their natal streams in order to spawn provides a mechanism by which
(A) pristine streams that are near polluted streams become polluted themselves
(B) the particular adaptations of a polluted stream’s salmon population can be preserved without dilution
(C) the number of salmon in pristine habitats decreases relative to the number in polluted streams
(D) an environmentally degraded stream could be recolonized by new salmon populations should the stream recover
(E) the extinction of the salmon populations that spawn in polluted streams is accelerated
@KarishmaB explanation:
The passage says: Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear.
This sentence means that straying is crucial because it provides a mechanism by which the current location can be repopulated (it is already populated so it can be repopulated) should the fish here disappear.
Say today some fish stray to other streams. Say after 1 month, the condition of this stream deteriorates such that all the fish in it die. After a few months, this stream is cleaned up and its waters can support life again. Then the fish that had strayed can be brought back here to repopulate these waters.
Passage tells us: Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted.
So some fish from stream A stray to stream B. Now stream B fish have some local adaptations. If too many fish from stream A come to stream B, those local adaptations could be lost. This could result in lower the overall fitness of subsequent generations."
GMATNINJA explanation:
[b]GMATNinja[/b]
"Think about the role of the words "should the stream recover." Here, they LIMIT the circumstances in which an environmentally degraded stream could be repopulated by straying.
The passage tells that low levels of straying mean that a "location can be repopulated should the fish there disappear." There are no limitations placed on why the fish disappeared in the first place, or what happened to the environment after that.
From this, you could make all kinds of inferences -- for example, if the fish disappeared because of over-fishing, then you could infer that straying would allow the location to be repopulated once fishing is limited again in the area.
Equally, you could infer that if the fish disappeared because of environmental degradation, then straying would allow the location to be repopulated once the environment recovers. This is what (D) tells us. Sure, it's just one circumstance out of many possible circumstances. But that limitation is totally fine -- we can still infer (D), so that's the correct answer to question 2."
Hello GMATNinja and @KrishmaB
From your explanations for the meaning of "Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear. Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted.", I understand as follows:
- A location (or environment/ stream/ habitat) had degraded because of some event (for example environmental degradation), so the fish in this location disappeared. But then this location recovered.
- Next, a low rate of new salmon fish stray to this location (instead of returning their natal stream because of this stream was degraded). Because of LOW RATE, this location is recolonized/ repopulated.
I am confused: If the fish in this location disappeared, there is no fish. Therefore, the new salmon fish do not interbreed with any existing fish. (interbreed with whom?) Therefore, low rate or high rate of straying does not matter with dillution in this location. In other words, any rate of straying can help this location to be recolonized.
Please help me to clear my mind.
Thank you very much
We are not talking about the same stream here.
Consider three different but neighbouring streams.
Stream A which is native to our fishA and is doing well.
Stream B gets overly polluted and all our fish pop dies there. Subsequently, stream B is cleaned.
Stream C is surviving but has high levels of mercury. The fish there have adapted to these high levels.
Now when fishA return from the ocean back to stream A, there may be some low level of straying into stream B. This is good for stream B because it will have fish again now. This explains "Low levels of straying are crucial, since the process provides a mechanism by which a location can be repopulated should the fish there disappear"
What if while fishA are returning, there is high level of straying to stream C? They breed with fishC (who are immune to high levels of mercury ) and produce fish that are not immune to these mercury levels. Most fish in stream C could then die. This explains "Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted."
) ) -- I agree that we don't care whether the pristine streams are affected by natural disaster or not. We are only concerned about the link between "human activity" and the lowering of overall Darwinian fitness. 
