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herb

by maihuna » Mon Dec 14, 2009 10:43 am
Q28:
Which of the following most logically completes the argument?
A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants. Agronomists studying the herb have discovered that it produces large amounts of histidine, an amino acid that, in test-tube solutions, renders these metals chemically inert. Possibly, therefore, the herb's high histidine production is what allows it to grow in metal-rich soils, a hypothesis that would gain support if ______.
A. histidine is found in all parts of the plant-roots, stem, leaves, and flowers
B. the herb's high level of histidine production is found to be associated with an unusually low level of production of other amino acids
C. others of the closely related group of plants are also found to produce histidine in large quantities
D. cultivation of the herb in soil with high concentrations of the metals will, over an extended period, make the soil suitable for plants to which the metals are toxic
E. the concentration of histidine in the growing herb declines as the plant approaches maturity
[spoiler]Answer:D/E[/spoiler][/spoiler]
Last edited by maihuna on Tue Dec 15, 2009 5:11 am, edited 1 time in total.
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by pandeyvineet24 » Mon Dec 14, 2009 11:36 am
i think the answer should be C. By POE, i think none of the other answer choices are relevant.
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by maihuna » Mon Dec 14, 2009 11:42 am
pandeyvineet24 wrote:i think the answer should be C. By POE, i think none of the other answer choices are relevant.
But C at best says there are other type of plants having this histidine, that helps no where to strengthen due to hestidine such herbs grow in toxic rich metal area...
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by KapTeacherEli » Mon Dec 14, 2009 12:52 pm
This is a classic cause/effect scenerio, repeated often on the GMAT. In this case, the possible cause is Histidine, leading to the effect of survival of the plant. But there is another key clue in this stimulus--that this herb is one of a family of herbs. That is a shift in scope, which indicates an assumption in the argument. The correct answer, we can predict, must therefore establish whether histidine is a possible explanation for not only the one herb but also its cousins, or whether something else about the family of plants aside from histidine is a likely cause.

For that reason, C will help us. If all of the family produces histidine, and all live in metal-rich soil, our explanation is highly plausible. However, if some of the species are living in the same toxic soil without histidine, the claim that this one plant requires the amino acid becomes suspect.
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by pandeyvineet24 » Mon Dec 14, 2009 1:04 pm
maihuna wrote:
pandeyvineet24 wrote:i think the answer should be C. By POE, i think none of the other answer choices are relevant.
But C at best says there are other type of plants having this histidine, that helps no where to strengthen due to hestidine such herbs grow in toxic rich metal area...
agree with you maihuna, but the opening statement of the argument states that this herb is similar to other plant species that survive in toxic environments. As per C these plants also generate histidine.
None of the other choices seems to be in scope.
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by maihuna » Tue Dec 15, 2009 5:15 am
KapTeacherEli wrote:This is a classic cause/effect scenerio, repeated often on the GMAT. In this case, the possible cause is Histidine, leading to the effect of survival of the plant. But there is another key clue in this stimulus--that this herb is one of a family of herbs. That is a shift in scope, which indicates an assumption in the argument. The correct answer, we can predict, must therefore establish whether histidine is a possible explanation for not only the one herb but also its cousins, or whether something else about the family of plants aside from histidine is a likely cause.

For that reason, C will help us. If all of the family produces histidine, and all live in metal-rich soil, our explanation is highly plausible. However, if some of the species are living in the same toxic soil without histidine, the claim that this one plant requires the amino acid becomes suspect.
Hi Eli, but no where does it mention that other family of herbs survive in metal rich soil. here is my take on this:

C First, the argument concerns ONE plant out of a group of related plants. The argument does not involve the other plants in that group. Second, the fact that histidine renders the toxic metals inert IN TEST-TUBE solutions does not mean that the herb releases histidine so as to render these same toxic metals inert in soil (and that's the ASSUMPTION here-that since histidine deactivates toxic metals in test-tubes, perhaps it does the same thing when produced and released by this particular herb in soil. The argument does NOT say that the plant, while growing in test-tube solutions, produces large amounts of histidine, thereby rendering the metals inert. We really need something that links the laboratory information to the real world and C does not provide it.

D If the herb produces a significant amount of histidine as a metabolic process, and if histidine renders the toxic metals inert in test-tubes, and if the cultivation of this particular herb in "toxic metal-rich" soil apparently renders the toxic metals in the soil inert (this is basically what Choice D states), then perhaps the herb's high histidine production is, in fact, what allows the herb itself to grow in metal-rich soils. :? :? :?
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by sadullaevd » Tue Dec 15, 2009 6:17 am
KapTeacherEli wrote:This is a classic cause/effect scenerio, repeated often on the GMAT. In this case, the possible cause is Histidine, leading to the effect of survival of the plant. But there is another key clue in this stimulus--that this herb is one of a family of herbs. That is a shift in scope, which indicates an assumption in the argument. The correct answer, we can predict, must therefore establish whether histidine is a possible explanation for not only the one herb but also its cousins, or whether something else about the family of plants aside from histidine is a likely cause.

For that reason, C will help us. If all of the family produces histidine, and all live in metal-rich soil, our explanation is highly plausible. However, if some of the species are living in the same toxic soil without histidine, the claim that this one plant requires the amino acid becomes suspect.
Great explanation, Eli.
I missed the "family" part.
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by KapTeacherEli » Wed Dec 16, 2009 8:50 pm
maihuna wrote: Hi Eli, but no where does it mention that other family of herbs survive in metal rich soil. here is my take on this:
A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants.

Easy to miss, but there it is!
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by tanviet » Thu Dec 17, 2009 12:13 am
"critical reasoning bible" book gave full explanation of cause-effect argurment

author see two thing happen at the same time and conclude that two things have causal relation.

the conclusion will be strengthened (weakened) if one of following situations exists

1, no cause, no effect (no cause, effect exist)

2,cause exists, effect exists (cause exist, effect dose not exist)

3, effect dose not create cause-causal relation is not reversed---one question in OG11 show this.

4. there is no third element which create effect. (there is third element which create effect)

C said case 2 above. the chemical (cause) exist in all relative plants which has the effect.
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by maihuna » Fri Dec 18, 2009 7:25 am
KapTeacherEli wrote:
maihuna wrote: Hi Eli, but no where does it mention that other family of herbs survive in metal rich soil. here is my take on this:
A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants.

Easy to miss, but there it is!
Eli, I think then the major issue is crossing out D on valid ground. On what logic to kill option D.?
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