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Understanding the passage
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.
• There is a certain cultivated herb, which is one of a group of closely related plants.
• These closely related group of plants grow well in soil with high levels of metals.
• Soil with high metallic content is toxic for most other plants.
Agronomists studying the growth of this herb have discovered that it produces large amounts of histidine, an amino acid that, in test-tube solutions, renders these metals chemically inert.
• Agronomists, who are studying the growth of this herb, have discovered that these herbs produce large quantities of histidine.
• Histidine is an amino acid.
• Histidine renders metallic chemicals inactive in test-tube solutions.
Hence, the herb's high histidine production must be the key feature that allows it to grow in metal-rich soils.
• Thus, the author concludes that the high histidine production in herbs is the main reason that allows these herbs to grow in metal-rich soils.
• The reason for the author's conclusion is that histidine renders metallic chemicals inactive, as proved in test-tube experiments.
Conclusion: A certain cultivated herbs' ability to produce high amounts of histidine is the main reason these herbs' can grow in metal-rich soils.
Pre-thinking
Falsification scenario
In what scenario – will the high histidine production in herbs NOT be the main reason that allows these herbs to grow in metal-rich soils.
Given that:
(i) These cultivated herbs belong to a group of closely related plants.
(ii) These plants thrive in soils with a high concentration of metals.
(iii) For most other plants, this high metallic content of the soil is toxic.
(iv) These herbs produce histidine in large amounts.
(v) Histidine renders metallic chemicals inactive, as proved in test-tube experiments.
Thought Process
Herbs, which belong to a group of closely related plants, can thrive in soils with a high concentration of metals, whereas, for most other plants, these metals are toxic. These groups of herbs must have something in common, which helps them thrive in soils with a high concentration of metals. According to Agronomists, this group of herbs produces large amounts of histidine, rendering metallic chemicals inactive. Therefore, histidine is the main reason why these herbs can thrive in metal-rich soils.
Falsification condition 1: What if most other plants can also produce large amounts of histidine?
In this scenario, histidine cannot be the main reason why herbs of a closely related group can thrive in metal-rich soils. The reason being that if most other groups of plants also produce a high amount of histidine, then those plants should also be able to thrive in metal-rich soils. This scenario would break the author's conclusion.
Assumption 1: Most other plants cannot produce large amounts of histidine.
Falsification scenario 2: What if the other plants in the group of closely related herbs produce some other type of chemicals other than histidine, which allows them to flourish in metal-rich soils?
In this scenario, it could be possible that the other chemicals are responsible for the survival of that group of related plants. This scenario breaks the conclusion.
Assumption 2: Other plants in the group of closely related herbs do not produce some other type of chemicals other than histidine, which allows them to flourish in metal-rich soils.
Falsification scenario 3: What if the other closely related plants have evolved to adapt to metal-rich soils?
In this scenario, histidine would not be the main reason why these herbs can thrive in metal-rich soils. This scenario would also break the conclusion.
Assumption 3: The other closely related plants have not evolved to adapt to metal-rich soils.
Answer Choice Analysis
(A) Whether the herb can thrive in soil that does not have high concentrations of the toxic metals INCORRECT
• This information is irrelevant to the passage because the passage is about the herb that survives in soil with a high concentration of toxic metals and if it is because of histidine present in the herb or not.
• Thus, this choice is incorrect
(B) Whether others of the closely related group of plants also produce histidine in large quantities CORRECT
• This choice is directly in line with our pre-thinking assumption 1.
• Variance test
o Yes - others of the closely related group of plants also produce histidine in large quantities
o This would prove that histidine is the main reason the herb can grow in metal-rich soil. This information strengthens our belief in the conclusion.
o No - others of the closely related group of plants did not produce histidine in large quantities
o This weakens our belief in the conclusion as there can be some other factor that is responsible for helping the herb grow in metal-rich soil.
• Hence, this option is the correct choice.
(C) Whether the herb's high level of histidine production is associated with an unusually low level of production of some other amino acid INCORRECT
• Even if histidine impacts the production of some other amino acids, it does not tell us whether histidine is/isn’t the key factor in the growth of the herb. The connection of an unusually low level of production of some other amino acid to the growth of the herb is ambiguous.
(D) Whether growing the herb in soil with high concentrations of the metals will, over time, reduce their concentrations in the soil INCORRECT
• The impact on the soil is irrelevant.
(E) Whether the concentration of histidine in the growing herb declines as the plant approaches maturity INCORRECT
• Even if we consider this a “yes,” it does not tell us whether histidine is the key factor in hindering the toxicity of the soil and helping the herb grow.
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.
• There is a certain cultivated herb, which is one of a group of closely related plants.
• These closely related group of plants grow well in soil with high levels of metals.
• Soil with high metallic content is toxic for most other plants.
Agronomists studying the growth of this herb have discovered that it produces large amounts of histidine, an amino acid that, in test-tube solutions, renders these metals chemically inert.
• Agronomists, who are studying the growth of this herb, have discovered that these herbs produce large quantities of histidine.
• Histidine is an amino acid.
• Histidine renders metallic chemicals inactive in test-tube solutions.
Hence, the herb's high histidine production must be the key feature that allows it to grow in metal-rich soils.
• Thus, the author concludes that the high histidine production in herbs is the main reason that allows these herbs to grow in metal-rich soils.
• The reason for the author's conclusion is that histidine renders metallic chemicals inactive, as proved in test-tube experiments.
Conclusion: A certain cultivated herbs' ability to produce high amounts of histidine is the main reason these herbs' can grow in metal-rich soils.
Pre-thinking
Falsification scenario
In what scenario – will the high histidine production in herbs NOT be the main reason that allows these herbs to grow in metal-rich soils.
Given that:
(i) These cultivated herbs belong to a group of closely related plants.
(ii) These plants thrive in soils with a high concentration of metals.
(iii) For most other plants, this high metallic content of the soil is toxic.
(iv) These herbs produce histidine in large amounts.
(v) Histidine renders metallic chemicals inactive, as proved in test-tube experiments.
Thought Process
Herbs, which belong to a group of closely related plants, can thrive in soils with a high concentration of metals, whereas, for most other plants, these metals are toxic. These groups of herbs must have something in common, which helps them thrive in soils with a high concentration of metals. According to Agronomists, this group of herbs produces large amounts of histidine, rendering metallic chemicals inactive. Therefore, histidine is the main reason why these herbs can thrive in metal-rich soils.
Falsification condition 1: What if most other plants can also produce large amounts of histidine?
In this scenario, histidine cannot be the main reason why herbs of a closely related group can thrive in metal-rich soils. The reason being that if most other groups of plants also produce a high amount of histidine, then those plants should also be able to thrive in metal-rich soils. This scenario would break the author's conclusion.
Assumption 1: Most other plants cannot produce large amounts of histidine.
Falsification scenario 2: What if the other plants in the group of closely related herbs produce some other type of chemicals other than histidine, which allows them to flourish in metal-rich soils?
In this scenario, it could be possible that the other chemicals are responsible for the survival of that group of related plants. This scenario breaks the conclusion.
Assumption 2: Other plants in the group of closely related herbs do not produce some other type of chemicals other than histidine, which allows them to flourish in metal-rich soils.
Falsification scenario 3: What if the other closely related plants have evolved to adapt to metal-rich soils?
In this scenario, histidine would not be the main reason why these herbs can thrive in metal-rich soils. This scenario would also break the conclusion.
Assumption 3: The other closely related plants have not evolved to adapt to metal-rich soils.
Answer Choice Analysis
(A) Whether the herb can thrive in soil that does not have high concentrations of the toxic metals INCORRECT
• This information is irrelevant to the passage because the passage is about the herb that survives in soil with a high concentration of toxic metals and if it is because of histidine present in the herb or not.
• Thus, this choice is incorrect
(B) Whether others of the closely related group of plants also produce histidine in large quantities CORRECT
• This choice is directly in line with our pre-thinking assumption 1.
• Variance test
o Yes - others of the closely related group of plants also produce histidine in large quantities
o This would prove that histidine is the main reason the herb can grow in metal-rich soil. This information strengthens our belief in the conclusion.
o No - others of the closely related group of plants did not produce histidine in large quantities
o This weakens our belief in the conclusion as there can be some other factor that is responsible for helping the herb grow in metal-rich soil.
• Hence, this option is the correct choice.
(C) Whether the herb's high level of histidine production is associated with an unusually low level of production of some other amino acid INCORRECT
• Even if histidine impacts the production of some other amino acids, it does not tell us whether histidine is/isn’t the key factor in the growth of the herb. The connection of an unusually low level of production of some other amino acid to the growth of the herb is ambiguous.
(D) Whether growing the herb in soil with high concentrations of the metals will, over time, reduce their concentrations in the soil INCORRECT
• The impact on the soil is irrelevant.
(E) Whether the concentration of histidine in the growing herb declines as the plant approaches maturity INCORRECT
• Even if we consider this a “yes,” it does not tell us whether histidine is the key factor in hindering the toxicity of the soil and helping the herb grow.
22 Oct 2020, 11:13
Kudos
Bookmarks
Dear IanStewart
Could you please help me with choice B vs. D dilemma? I can see why B is the correct answer, yet it doesn’t look like other correct answers to evaluate-type problems.
Regarding B:
With “yes”, B says that other similar plants also produce a lot of histidine. Sure, this info lends some weigh to the conclusion, but still it doesn’t necessarily mean that histidine is the “key” feature. In other words, this info doesn’t inhibit the likelihood of another “key” feature that is shared by all similar plants and that makes producing histidine a peripheral.
With “no”, B says that other similar plants don’t produce a lot of histidine. While with this info the conclusion may wane, those similar plants still might have different “key features”, and producing histedine can be “key” only for the one under consideration. Therefore, I concluded that the impact of choice B on the conclusion is barely measurable. Apparently, I was wrong. So, why can B be correct even if it leaves such loopholes?
Regarding D:
I eliminated B also because D seemed to have a greater impact on the argument. While solving the problem, I barely comprehended what “chemically inert” exactly means, and thus construed it as “corrupt the metal and thereby reduce its concentrations”. Therefore, D seemed to make more sense.
Indeed, if histedine reduced the concentrations of metal, we could conclude that the plant this way makes its environment less toxic and more favorable. If the concentrations didn’t decrease, then probably the plant used other “key” feature to survive while emitting histedine not through roots but through leaves or other upper part, thereby barely impacting the concentrations in the soil.
So, I am curious would D be a contender if “chemically inert” meant “reduce the concentration”?
Very much hope for your elucidation. Thank you very much beforehand!
Could you please help me with choice B vs. D dilemma? I can see why B is the correct answer, yet it doesn’t look like other correct answers to evaluate-type problems.
Regarding B:
With “yes”, B says that other similar plants also produce a lot of histidine. Sure, this info lends some weigh to the conclusion, but still it doesn’t necessarily mean that histidine is the “key” feature. In other words, this info doesn’t inhibit the likelihood of another “key” feature that is shared by all similar plants and that makes producing histidine a peripheral.
With “no”, B says that other similar plants don’t produce a lot of histidine. While with this info the conclusion may wane, those similar plants still might have different “key features”, and producing histedine can be “key” only for the one under consideration. Therefore, I concluded that the impact of choice B on the conclusion is barely measurable. Apparently, I was wrong. So, why can B be correct even if it leaves such loopholes?
Regarding D:
I eliminated B also because D seemed to have a greater impact on the argument. While solving the problem, I barely comprehended what “chemically inert” exactly means, and thus construed it as “corrupt the metal and thereby reduce its concentrations”. Therefore, D seemed to make more sense.
Indeed, if histedine reduced the concentrations of metal, we could conclude that the plant this way makes its environment less toxic and more favorable. If the concentrations didn’t decrease, then probably the plant used other “key” feature to survive while emitting histedine not through roots but through leaves or other upper part, thereby barely impacting the concentrations in the soil.
So, I am curious would D be a contender if “chemically inert” meant “reduce the concentration”?
Very much hope for your elucidation. Thank you very much beforehand!
22 Oct 2020, 11:56
Kudos
Bookmarks
JonShukhrat
but still it doesn’t necessarily mean that histidine is the “key” feature.
We learn the one surviving herb produces "large amounts" ("large" presumably relative to the average plant that dies in the soil) of histidine, which basically defuses toxic metals in soil. That seems a very plausible explanation for its survival to me -- I find it hard to imagine that this plant has a second unusual feature that could be more "key" to its survivability in the soil. There are at least two open questions, reading the stem:
• are the laboratory conditions in the test tube replicated when the plant is actually out in the wild?
• assuming (a kind of an Occam's Razor assumption) this one herb survives for the same reason as the "closely related" plants, do those related plants also produce histidine?
I assumed reading the question that I'd want evidence of the first item above. At first glance, D might seem to address that question, but it's deceptive -- it does not, which I'll get to below. But the second point is also important: if this family of plants all produce histidine, and other plants (the ones that die in the soil) do not, then it seems plausible, because we have a cogent explanation for the action of histidine on the toxic metals, to conclude histidine plays an important role here. If instead we discovered the other closely related plants produce very little histidine, then because they are close relatives, it would be reasonable to assume they share some other feature that explains why they all survive.
It does matter a lot here that we have an explanation that very plausibly connects histidine production and survival in the soil. Without that explanation, noting a similar feature among these closely related plants wouldn't be meaningful; they presumably have a lot of things in common, most of which are irrelevant to how successfully they survive metal toxicity.
D can't be right because when we make a metal "chemically inert", it's still a metal. It's just not reacting with anything. If, though, answer D told us that the effect observed in the test tube is also observed in the soil, it would be useful, because we can't be sure of that without real world evidence. Then the question would have two promising answers, a situation you won't encounter in any official source (though it's a situation I often encounter in prep company questions).
