Every culture that has adopted the cultivation of maize—also known as

Question

LSAT June 2006, Passage #4: Maize 
Maize is just another word for corn, so at first this passage doesn’t look too difficult. Indeed, the first paragraph is fairly easy to understand, as it lays out the importance of maize to the cultures that cultivated it. After the first paragraph, however, the discussion turns extremely detailed and covers the physical science behind why maize is so bountiful. Corn never tasted so bad. 
   Every culture that has adopted the cultivation of maize—also known as corn—has been radically changed by it. This crop reshaped the cultures of the Native Americans who first cultivated it, leading to such developments as the adoption of agrarian and in some cases urban lifestyles, and much of the explosion of European populations after the fifteenth century was driven by the introduction of maize together with another crop from the Americas, potatoes. The primary reason for this plant’s profound influence is its sheer productivity. With maize, ancient agriculturalists could produce far more food per acre than with any other crop, and early Central Americans recognized and valued this characteristic of the plant. But why are maize and a few similar crops so much more bountiful than others? Modern biochemistry has revealed the physical mechanism underlying maize’s impressive productivity.

To obtain the hydrogen they use in the production of carbohydrates through photosynthesis, all plants split water into its constituent elements, hydrogen and oxygen. They use the resultant hydrogen to form one of the molecules they need for energy, but the oxygen is released into the atmosphere. During photosynthesis, carbon dioxide that the plant takes in from the atmosphere is used to build sugars within the plant. An enzyme, rubisco, assists in the sugar forming chemical reaction. Because of its importance in photosynthesis, rubisco is arguably the most significant enzyme in the world. Unfortunately, though, when the concentration of oxygen relative to carbon dioxide in a leaf rises to a certain level, as can happen in the presence of many common atmospheric conditions, oxygen begins to bind competitively to the enzyme, thus interfering with the photosynthetic reaction.

Some plants, however, have evolved a photosynthetic mechanism that prevents oxygen from impairing photosynthesis. These plants separate the places where they split water atoms into hydrogen and oxygen from the places where they build sugars from carbon dioxide. Water molecules are split, as in all plants, in specialized chlorophyll-containing structures in the green leaf cells, but the rubisco is sequestered within airtight tissues in the center of the leaf. The key to the process is that in these plants, oxygen and  all other atmospheric gases  are excluded from the cells containing rubisco. These cells, called the bundle sheath cells, surround the vascular structures of the leaf—structures that function analogously to human blood vessels. Carbon dioxide, which cannot enter these cells as a gas, first under goes a series of reactions to form an intermediary, non gas molecule named C-4 for the four carbon atoms it contains. This molecule enters the bundle sheath cells and there undergoes reactions that release the carbon dioxide that will fuel the production of carbohydrates (e.g., sugars).Taking its name from the intermediary molecule, the entire process is called C-4 photosynthesis. Such C-4 plants as sugar cane, rice, and maize are among the world’s most productive crops.   1 
 A 
 1. Which one of the following most accurately states the main point of the passage?

(A) The greater productivity of maize, as compared with many other crops, is due to its C-4 photosynthetic process, in which the reactions that build sugars are protected from the effects of excess oxygen. 
(B) Because of their ability to produce greater quantities and higher qualities of nutrients, those plants, including maize, that use a C-4 photosynthetic process have helped to shape the development of many human cultures. 
(C) C-4 photosynthesis, which occurs in maize, involves a complex sequence of chemical reactions that makes more efficient use of available atmospheric hydrogen than do photosynthetic reactions in non-C-4 plants. 
(D) The presence of the enzyme rubisco is a key factor in the ability of C-4 plants, including maize, to circumvent the negative effects of gases such as oxygen on the production of sugars in photosynthesis. 
(E) Some of the world’s most productive crop plants, including maize, have evolved complex, effective mechanisms to prevent atmospheric gases that could bind competitively to rubisco from entering the plants’ leaves.

2 
 B 
 2. Which one of the following most accurately describes the organization of the material presented in the second and third paragraphs of the passage?

(A) The author suggests that the widespread cultivation of a particular crop is due to its high yield, explains its high yield by describing the action of a particular enzyme in that crop, and then outlines the reasons for the evolution of that enzyme. 
(B) The author explains some aspects of a biochemical process, describes a naturally occurring hindrance to that process, and then describes an evolutionary solution to that hindrance in order to explain the productivity of a particular crop. 
(C) The author describes a problem inherent in certain biochemical processes, scientifically explains two ways in which organisms solve that problem, and then explains the evolutionary basis for one of those solutions. 
(D) The author describes a widespread cultural phenomenon involving certain uses of a type of plant, explains the biochemical basis of the phenomenon, and then points out that certain other plants may be used for similar purposes. 
(E) The author introduces a natural process, describes the biochemical reaction that is widely held to be the mechanism underlying the process, and then argues for an alternate evolutionary explanation of that process.

3 
 B 
 3. Assuming that all other relevant factors remained the same, which one of the following, if it developed in a species of plant that does not have C-4 photosynthesis, would most likely give that species an advantage similar to that which the author attributes to C-4plants?

(A) Water is split into its constituent elements in specialized chlorophyll-containing structures in the bundle sheath cells. 
(B) An enzyme with which oxygen cannot bind performs the role of rubisco. 
(C) The vascular structures of the leaf become impermeable to both carbon dioxide gas and oxygen gas. 
(D) The specialized chlorophyll-containing structures in which water is split surround the vascular structures of the leaf. 
(E) An enzyme that does not readily react with carbon dioxide performs the role of rubisco in the green leaf cells.

4 
 D 
 4. The author’s reference to “all other atmospheric gases” ( Highlighted ) plays which one of the following roles in the passage?

(A) It indicates why certain atmospheric conditions can cause excess oxygen to build up and thus hinder photosynthesis in non-C-4 plants as described in the previous paragraph. 
(B) It supports the claim advanced earlier in the paragraph that oxygen is not the only atmospheric gas whose presence in the leaf can interfere with photosynthesis. 
(C) It supports the conclusion that non-C-4 photosynthesis makes use of several atmospheric gases that C-4 photosynthesis does not use. 
(D) It explains why carbon dioxide molecules undergo the transformations described later in the paragraph before participating in photosynthesis in C-4 plants. 
(E) It advances a broader claim that oxygen levels remain constant in C-4 plants in spite of changes in atmospheric conditions.

5 
 D 
 5. The passage contains information sufficient to justify inferring which one of the following? 
 
(A) In rice plants, atmospheric gases are prevented from entering the structures in which water is split into its constituent elements. 
(B) In rice plants, oxygen produced from split water molecules binds to another type of molecule before being released into the atmosphere. 
(C) Rice is an extremely productive crop that nourishes large segments of the world’s population and is cultivated by various widely separated cultures. 
(D) In rice plants, rubisco is isolated in the bundle sheath cells that surround the vascular structures of the leaves. 
(E) Although rice is similar to maize in productivity and nutritive value, maize is the more widely cultivated crop.

6 
 E 
 6. The author of the passage would be most likely to agree with which one of the following statements?

(A) Maize’s impressive productivity cannot be understood without an understanding of its cultural influences. 
(B) Maize is an example of a plant in which oxygen is not released as a by-product of photosynthesis. 
(C) Maize’s high yields are due not only to its use of C-4 but also to its ability to produce large quantities of rubisco. 
(D) Until maize was introduced to Europeans by Native Americans, European populations lacked the agricultural techniques required for the cultivation of C-4 plants. 
(E) Maize’s C-4 photosynthesis is an example of an effective evolutionary adaptation that has come to benefit humans

7 
 A 
 7. The passage provides the most support for which one of the following statements? 
 
(A) In many plants, rubisco is not isolated in airtight tissues in the center of the leaf. 
(B) A rubisco molecule contains four carbon atoms. 
(C) Rubisco is needed in photosynthesis to convert carbon dioxide to a nongas molecule. 
(D) In maize, rubisco helps protect against the detrimental effects of oxygen buildup in the leaves. 
(E) Rubisco’s role in the C-4 process is optimized when oxygen levels are high relative to carbon dioxide levels.

Source:   LSAT Official PrepTest 49   ( June 2006 ) 
 Difficulty Level:   700

As requested I am posting a brutal RC passage from an old LSAT exam. This passage has been voted as one of the top 10 most brutal passages to ever appear on the lsat exams in the last 30 years. This passage gave alot of students trouble. I found it during my research on brutal RCs. I started looking into LSAT RCs after GMATNinja mentioned how much tougher they were than GMAT passages and attempting these would take my skills to the next level. These are very high quality passages, designed to challenge you to the fullest.

I can confidently say that after doing about a dozen of these I already feel a huge improvement in my reading comprehension. Whats different about these passages is that they are much more detailed, they are longer and require a great deal more concentration than the average GMAT passage. The questions are also a tid bit tougher and wordier. So here's the first one. Shoutout to Stonecold warriorguy abhimahna duahsolo vyshak and gmatexam349 shailabh & hazelnut Good luck!

Remember you are allowed to have on avg 8-10 minutes to answer all the question during the lsat exam but you can take 15-20 minutes here.

New Project RC Butler 2019  -  Practice 2 RC Passages Everyday   
Passage # 266, Date : 13-Aug-2019
 This post is a part of New Project RC Butler 2019 .  Click here for Details

tarunanandani · Answer

1. Which one of the following most accurately states the main point of the passage?

(A) The greater productivity of maize, as compared with many other crops, is due to its C-4 photosynthetic process, in which the reactions that build sugars are protected from the effects of excess oxygen. --- Correct , aptly describes the gist of the passage. The first para introduces the high productivity question and the subsequent paras provide the answer to that question.

(B) Because of their ability to produce greater quantities and higher qualities of nutrients, those plants, including maize, that use a C-4 photosynthetic process have helped to shape the development of many human cultures. --- Incorrect , partial scope. Moreover, the passage doesn't focus on why some plants helped to reshape human cultures rather focuses on reason for high productivity.

(C) C-4 photosynthesis, which occurs in maize, involves a complex sequence of chemical reactions that makes more efficient use of available atmospheric hydrogen than do photosynthetic reactions in non-C-4 plants. --- Incorrect , distortion of details.

(D) The presence of the enzyme rubisco is a key factor in the ability of C-4 plants, including maize, to circumvent the negative effects of gases such as oxygen on the production of sugars in photosynthesis. --- Incorrect , same as C.

(E) Some of the world’s most productive crop plants, including maize, have evolved complex, effective mechanisms to prevent atmospheric gases that could bind competitively to rubisco from entering the plants’ leaves. --- Incorrect , partial scope. The passage does mention evolution of some plants but it does in order to answer the question of high productivity.

2. Which one of the following most accurately describes the organization of the material presented in the second and third paragraphs of the passage?

(A) The author suggests that the widespread cultivation of a particular crop is due to its high yield, explains its high yield by describing the action of a particular enzyme in that crop, and then outlines the reasons for the evolution of that enzyme. --- Incorrect , 'the widespread cultivation of a particular crop is due to its high yield' is mentioned in 1st para.

(B) The author explains some aspects of a biochemical process, describes a naturally occurring hindrance to that process, and then describes an evolutionary solution to that hindrance in order to explain the productivity of a particular crop. --- Correct , The 2nd para describes photosynthesis and mentions a problem, relatively high oxygen levels, to the process. The 3rd para then describes an evolution, isolation of enzyme from atmospheric gases, to overcome the hindrance.

(C) The author describes a problem inherent in certain biochemical processes, scientifically explains two ways in which organisms solve that problem, and then explains the evolutionary basis for one of those solutions. --- Incorrect , no two ways have been described. Only one evolution is mentioned.

(D) The author describes a widespread cultural phenomenon involving certain uses of a type of plant, explains the biochemical basis of the phenomenon, and then points out that certain other plants may be used for similar purposes. --- Incorrect , usage of plants has not been discussed.

(E) The author introduces a natural process, describes the biochemical reaction that is widely held to be the mechanism underlying the process, and then argues for an alternate evolutionary explanation of that process. --- Incorrect , no such argument is presented in the two paragraphs. No debate is mentioned on whether the biochemical reaction is widely held to be the mechanism underlying the process.

3. Assuming that all other relevant factors remained the same, which one of the following, if it developed in a species of plant that does not have C-4 photosynthesis, would most likely give that species an advantage similar to that which the author attributes to C-4plants?

Reference lines: (2nd para)'Unfortunately, though, when the concentration of oxygen relative to carbon dioxide in a leaf rises to a certain level, as can happen in the presence of many common atmospheric conditions, oxygen begins to bind competitively to the enzyme, thus interfering with the photosynthetic reaction'...(3rd para)'The key to the process is that in these plants, oxygen and all other atmospheric gases are excluded from the cells containing rubisco.'

So, we need to find an alternative such that oxygen doesn't interfere with photosynthesis. 
Only  option B  provides such a solution and hence is the correct answer.

(B) An enzyme with which oxygen cannot bind performs the role of rubisco.

4. The author’s reference to “all other atmospheric gases”in line 46 plays which one of the following roles in the passage?

Reference lines: 'The key to the process is that in these plants, oxygen and all other atmospheric gases are excluded from the cells containing rubisco...Carbon dioxide, which cannot enter these cells as a gas, first under goes a series of reactions to form an intermediary, non gas molecule named C-4 for the four carbon atoms it contains.'

Takeaway: Not only oxygen, but also other gases such as carbon dioxide can't reach the enzyme 'rubisco' and since carbon dioxide is essential for photosynthesis it must reach rubisco through some transformation, C-4.
 Option D  aptly describes this role and hence is the correct answer.

(D) It explains why carbon dioxide molecules undergo the transformations described later in the paragraph before participating in photosynthesis in C-4 plants.

5. The passage contains information sufficient to justify inferring which one of the following?

(A) In rice plants, atmospheric gases are prevented from entering the structures in which water is split into its constituent elements. --- Incorrect , distortion of details. Gases are prevented to reach rubisco.

(B) In rice plants, oxygen produced from split water molecules binds to another type of molecule before being released into the atmosphere. --- Incorrect , distortion of facts. Oxygen binds with rubisco in non C-4 plants and rice is mentioned as a C-4 plant.

(C) Rice is an extremely productive crop that nourishes large segments of the world’s population and is cultivated by various widely separated cultures. --- Incorrect , not supported by the passage. Corn instead of rice is mentioned to be such case.

(D) In rice plants, rubisco is isolated in the bundle sheath cells that surround the vascular structures of the leaves. --- Correct , Since, rice is an example of C-4 plant so this can be properly inferred from the passage.

(E) Although rice is similar to maize in productivity and nutritive value, maize is the more widely cultivated crop. --- Incorrect , not supported by the passage. Cultivation of rice is not discussed.

6. The author of the passage would be most likely to agree with which one of the following statements?

(A) Maize’s impressive productivity cannot be understood without an understanding of its cultural influences. --- Incorrect , an evolution is describe to answer reason for high productivity.
(B) Maize is an example of a plant in which oxygen is not released as a by-product of photosynthesis. --- Incorrect , distortion of facts. oxygen is released but is isolated from rubisco.
(C) Maize’s high yields are due not only to its use of C-4 but also to its ability to produce large quantities of rubisco. --- Incorrect , same as B. quantity of rubisco is not mentioned.
(D) Until maize was introduced to Europeans by Native Americans, European populations lacked the agricultural techniques required for the cultivation of C-4 plants. --- Incorrect , not supported by the passage.
(E) Maize’s C-4 photosynthesis is an example of an effective evolutionary adaptation that has come to benefit humans. --- Correct , by POE. Moreover, the passage mentions that an evolution led to high productivity of the crop, Maize and that this crop reshaped the cultures of the Native Americans.

7. The passage provides the most support for which one of the following statements?

(A) In many plants, rubisco is not isolated in airtight tissues in the center of the leaf. --- Correct , Only C-4 plants, rice sugar cane, corn, have such isolation
(B) A rubisco molecule contains four carbon atoms. --- Incorrect , distortion of details. CO2 changes its form to C-4 to reach rubisco.
(C) Rubisco is needed in photosynthesis to convert carbon dioxide to a nongas molecule. --- Incorrect , same as B.
(D) In maize, rubisco helps protect against the detrimental effects of oxygen buildup in the leaves. --- Incorrect , false. Isolation helps to prevent the damage.
(E) Rubisco’s role in the C-4 process is optimized when oxygen levels are high relative to carbon dioxide levels. --- Incorrect , opposite to the presented facts in the passage.

Diya52 · Answer

Hi  SajjadAhmad ,

Can you please post the explanation for Q4?

zoezhuyan · Answer

anyone can help Q3, 
I have not totally gotten what Q3 asked.

no mentioned how choose the answer.

Sajjad1994 · Answer

Explanation

4. The author’s reference to “all other atmospheric gases” ( Highlighted ) plays which one of the following roles in the passage?

Difficulty Level:   700

Explanation

How does the author’s reference to  “all other atmospheric gases”  fit into the rest of the passage? It has to have some function, otherwise it wouldn’t be there. The key to finding that function will be the context. With a bit of research, we find our answer just two sentences later. In passage, we learn that  “carbon dioxide, which cannot enter these cells as a gas, first undergoes a series of reactions to form an intermediary, nongas molecule named C-4.”  That’s why it’s important that the bundle sheath cells are impermeable to all gases: it explains why the chemical transformation of carbon dioxide into C-4 is necessary. We find this in (D).

(A)  There is no explanation given anywhere in the passage for why certain atmospheric conditions cause excess oxygen to build up.

(B)  There is no claim advanced that other gases can interfere with photosynthesis, either earlier in the paragraph or anywhere else in the passage.

(C)  The conclusion that non-C-4 photosynthesis makes use of atmospheric gases other than those used in C-4 photosynthesis never appears in the passage.

(E)  The passage makes no claim about oxygen levels in C-4 plants.

Answer: D

Hope it helps

Sajjad1994 · Answer

Explanation

3. Assuming that all other relevant factors remained the same, which one of the following, if it developed in a species of plant that does not have C-4 photosynthesis, would most likely give that species an advantage similar to that which the author attributes to C-4plants?

Difficulty Level:   650

Explanation

Ideally, as we first read through this passage, we’d treat the lengthy, technical details in  paragraph 2 and paragraph 3  as a trap. We don’t really need to understand these details to understand the author’s argument, and their dense, scientific nature makes it difficult and time-consuming for most examinees to slog through them. Besides, those details aren’t going to get us any points, unless there’s a question that requires us to use them. But now we’ve arrived at just such a question, so we’ll start to delve.

Of course, that doesn’t mean we’ll blindly start reading through the details of the passage—we can still use the question stem to guide our research. We’re looking for an evolutionary development that would give plants an advantage similar to that enjoyed by C-4 plants, so we’re looking for the details of how exactly C-4 photosynthesis conveys its advantages. Our Roadmap points us to  paragraph 3 , where the process of C-4 photosynthesis is described. Not long into that paragraph,  line 37  signals that we’ve found what we’re looking for,  “the key to that process.”  C-4 photosynthesis is so advantageous because oxygen, which interfered with normal photosynthesis by binding with rubisco, is excluded from the airtight cells containing the enzyme. We can conclude any other adaptation that keeps oxygen away from rubisco will give a species a similar advantage, and we find such an adaptation in (B), which dispenses with rubisco altogether in favor of a less temperamental enzyme.

(A)  is a 180. According to lines 38–39, the  “bundle sheath cells”  are the cells containing rubisco. If a plant separated water into its constituent parts within those cells, the rubisco would come into contact with more oxygen, not less.

(C)  Making the structures of the leaf impermeable to oxygen would help, but if they were impermeable to carbon dioxide as well, the plant would have no fuel from which to build sugars. This adaptation wouldn’t help.

(D)  This adaptation distorts the process of C-4 photosynthesis, in which  “the bundle sheath cells   surround the vascular structures of the leaf”

(E)  would hinder photosynthesis, since rubisco is the enzyme which produces sugar by reacting with carbon dioxide. A less reactive enzyme would necessarily be less effective.

Answer: B

Hope it helps

auradediligodo · Answer

Hi everyone,
Solved this one in 18 minutes.

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P1

Paragraph one starts with saying that maize has the ability to radically change a culture. In some case maize led to the development of agrarian or even urban lifestyles. This change can be seen in the native American population and in some European populations.

The reason why maize can lead to such radical change is that its productivity is far superior than the productivity of most other crops. It is said that the yield per acre is higher than other crops' yield per acre.

Finally we are told that some biochemist were able to solve the mystery behind this amazing productivity of maize.

Brief summary:  Maize is a very productive crop and why

P2

Paragraph 2, as we could imagine, deeps into the scientific aspects of maize.

It starts with explaining how photosynthesis and its inherent processes work. 
First we are given that hydrogen is used to produce carbohydrates and that in order to do so a plant gives water to its constituents: oxygen and hydrogen.
We also know that during the photosynthesis hydrogen is related to the production of energy. 
After that water is given to the plant constituents hydrogen is used for energy production while oxygen is released into the air.
Then we are given that the plant during photosynthesis absorbs carbon dioxide from the atmosphere in order to build sugar in the plant.
In the context of the sugar production we also know that an enzyme called Rubisco plays an important role and for its role it is considered as the most important enzyme in the world.
Lastly paragraph 2 introduces a contrast according to which if the ratio of oxygen to carbon dioxide overpasses a certain limit, oxygen binds with Rubisco and hence interferes with the sugar production.

Brief summary:  Photosynthesis process explained

P3

No need to say this is the most complex paragraph of the passage.

Last paragraph ended with the presentation of a problem, that is the impairment of the sugar production by oxygen binding with Rubisco.
This paragraph starts with saying that there are some crops, like maize, that have a special photosynthetic system that allows them to avoid this sort of trouble.
The logic of this mechanism is that the area where Rubisco interacts with carbon dioxide for the sugar production and the area where the plant gives water to hydrogen and oxygen are separated from each others. 
We are also given that oxygen and hydrogen receive water in chlorophyll structures while rubisco tends to be at the center of the leaf surrounded by the leaf vascular system and a system of airtight cells.
The cells where rubisco is present are also called bundle sheet cells and these cells don't allow atmospheric gasses to penetrate. 
So how could carbon dioxide, an atmospheric gas, get into such cells to start the sugar production with Rubisco?
In order to do so carbon dioxide is transformed into a non gas named C-4. 
After this transformation the new non gas C-4 can enter the bundle sheet cells and start the sugar production with rubisco.
The overall process is named after the non gas C-4.

Brief summary:  How certain crops like maize stop oxygen from binding to rubisco

Main point

The main point of the passage is to illustrate how maize is one of the most productive crops and how it overcomes a common problem related to the sugar production during the photosynthesis.

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1. Which one of the following most accurately states the main point of the passage?

Pre-thinking

Main point question

Refer to main point and summaries above

(A)   The greater productivity of maize, as compared with many other crops, is due to its C-4 photosynthetic process, in which the reactions that build sugars are protected from the effects of excess oxygen. 
 this is the correct answer as it focuses on elements that come from all the paragraphs

(B) Because of their ability to produce greater quantities and higher qualities of nutrients, those plants, including maize, that use a C-4 photosynthetic process have helped to shape the development of many human cultures. 
 Option B seems tempting but it is wrong for a couple of reasons: the first one is that it talks generally about plants and not specifically about maize. Secondly the focus is more on the scientific side than on the effects on development of cultures

(C) C-4 photosynthesis, which occurs in maize, involves a complex sequence of chemical reactions that makes  more efficient use of available atmospheric hydrogen  than do photosynthetic reactions in non-C-4 plants. 
 Too specific to be the main point

(D) The presence of the enzyme rubisco  is a key factor in the ability of C-4 plants, including maize, to circumvent the negative effects  of gases such as oxygen on the production of sugars in photosynthesis. 
 Wrong information and far too specific to be the main point

(E) Some of the world’s most productive crop plants, including maize, have evolved complex, effective mechanisms to prevent atmospheric gases that could bind competitively to rubisco from entering the plants’ leaves. 
 Too general statement given the fact that we are talking about maize

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2. Which one of the following most accurately describes the organization of the material presented in the second and third paragraphs of the passage?

Pre-thinking

Structure question

I the second paragraph the process of photosynthesis is explained and a drawback is outlined. In the third paragraph we are given how some plants, including maize, overcome that drawback

(A) The author suggests that the widespread cultivation of a particular crop  is due to its high yield , explains its high yield by describing the action of a particular enzyme in that crop, and then outlines the reasons for the evolution of that enzyme. 
 A contains elements of P1

(B)   The author explains some aspects of a biochemical process, describes a naturally occurring hindrance to that process, and then describes an evolutionary solution to that hindrance 
in order to explain the productivity of a particular crop. 
 In line with pre-thinking

(C) The author describes a problem inherent in certain biochemical processes, scientifically explains   two ways   in which organisms solve that problem, and then explains the evolutionary basis for one of those solutions. 
  not in line with pre-thinking

(D) The author describes  a widespread cultural phenomenon  involving certain uses of a type of plant, explains the biochemical basis of the phenomenon,  and then points out that certain other plants may be used for similar purposes.  
 not in line with pre-thinking

(E) The author introduces a natural process, describes the biochemical reaction that is widely held to be the mechanism underlying the process,  and then argues for an alternate evolutionary explanation of that process. 
 not in line with pre-thinking

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3. Assuming that all other relevant factors remained the same, which one of the following, if it developed in a species of plant that does not have C-4 photosynthesis, would most likely give that species an advantage similar to that which the author attributes to C-4plants?

Pre-thinking

Analogous statement question

So our task here is to identify how other plants that don't have C-4 photosynthesis will have a similar advantage. So the advantage is that oxygen does not interfere with rubisco and the production of sugar. This result is made possible by separating Rubisco and the areas where the plants gives water to hydrogen and oxygen. Let's see if an option choice presents this mechanism as well.

(A) Water is split into its constituent elements in specialized chlorophyll-containing structures  in the bundle sheath cells.  
 The bundle sheath cells are where rubisco is

(B) An enzyme with which oxygen cannot bind performs the role of rubisco. 
 Wonderful

(C) The vascular structures of the leaf become impermeable to both carbon dioxide gas and oxygen gas. 
 This works against us

(D) The specialized chlorophyll-containing structures in which water is split surround the vascular structures of the leaf. 
 Does not help

(E) An enzyme that does not readily react with carbon dioxide performs the role of rubisco in the green leaf cells.
 The key is that rubisco or a similar enzyme does not react with oxygen

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4. The author’s reference to “all other atmospheric gases” (Highlighted) plays which one of the following roles in the passage?

Pre-thinking

Role question

We are in paragraph 3 where the author is explaining how the C-4 process impedes to oxygen to reach the cells where rubisco is. 
The usage of all other atmospheric gases might mean few things: it could be that there are other gases other than oxygen which might impede the sugar production OR the mention might serve to puzzle us because we know that carbon dioxide is a gas and that C-4 mechanism blocks all the gas from entering the cells where rubisco lies. So The mention might prepare us to receive more information that explains how carbon dioxide gets in the cells where rubisco is.

(A) It indicates why certain atmospheric conditions can cause excess oxygen to build up and thus hinder photosynthesis in non-C-4 plants as described in the previous paragraph. 
 Nothing of the sort

(B) It supports the claim advanced earlier in the paragraph that oxygen is not the only atmospheric gas whose presence in the leaf can interfere with photosynthesis. 
 earlier in the passage nothing of the sort is mentioned

(C) It supports the conclusion that non-C-4 photosynthesis makes use of several atmospheric gases that C-4 photosynthesis does not use. 
 non C-4 photosynthesis is not detailed in the passage and we are not given that it uses more gases than C-4 photosynthesis. Actually they both use the same except for the fact that carbon dioxide is converted into an intermediary gas

(D)   It explains why carbon dioxide molecules undergo the transformations described later in the paragraph before participating in photosynthesis in C-4 plants. 
 In line with the second pre-though role of pre-thinking

(E) It advances a broader claim that oxygen levels remain constant in C-4 plants in spite of changes in atmospheric conditions.
 Cannot infer this statement

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5. The passage contains information sufficient to justify inferring which one of the following?

Pre-thinking

Inference question

Instead of pre-thinking all the inferences possible let's evaluate all the statements

(A) In rice plants, atmospheric gases are prevented from entering the structures in which water is split into its constituent elements. 
 Rice has a C-4 photosynthesis as maize has. But in C-4 photosynthesis the gas are prevented from entering the cells where rubisco is

(B) In rice plants, oxygen produced from split water molecules binds to another type of molecule before being released into the atmosphere. 
 Not mentioned

(C) Rice is an extremely productive crop that nourishes large segments of the world’s population and is cultivated by various widely separated cultures. 
 This statement is too general and extreme to be inferred

(D)   In rice plants, rubisco is isolated in the bundle sheath cells that surround the vascular structures of the leaves. 
 Correct as this is what happens in C-4 photosynthesis

(E) Although rice is similar to maize in productivity and nutritive value, maize is the more widely cultivated crop.
 Cannot be inferred

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6. The author of the passage would be most likely to agree with which one of the following statements?

Pre-thinking

Inference question

Let's evaluate the statements one by one

(A) Maize’s impressive productivity cannot be understood without an understanding of its cultural influences. 
   au contraire   we could understand its productivity from a scientific point of view

(B) Maize is an example of a plant in which oxygen is not released as a by-product of photosynthesis. 
 Probably it is released

(C) Maize’s high yields are due not only to its use of C-4 but also to its ability to produce large quantities of rubisco. 
 We don't have information enough to infer this

(D) Until maize was introduced to Europeans by Native Americans, European populations lacked the agricultural techniques required for the cultivation of C-4 plants. 
 we don't know whether there are requirements in terms of techniques to cultivate C-4 plants

(E)   Maize’s C-4 photosynthesis is an example of an effective evolutionary adaptation that has come to benefit humans
 C-4 photosynthesis indeed is an adaptation and indeed it has benefitted humas

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7. The passage provides the most support for which one of the following statements?

Pre-thinking

Inference question

let's evaluate the options one by one

(A)   In many plants, rubisco is not isolated in airtight tissues in the center of the leaf. 
 Usually we know that rubisco is isolated in plants which perform C-4 photosynthesis. So in the other plants, which we know to be many, rubisco may not be isolated in such way

(B) A rubisco molecule contains four carbon atoms. 
 That is carbon dioxide when it turns into an intermediary gas

(C) Rubisco is needed in photosynthesis to convert carbon dioxide to a nongas molecule. 
 No, rubisco is not needed to do that

(D) In maize, rubisco helps protect against the detrimental effects of oxygen buildup in the leaves. 
 Rubisco's function is to produce sugar with carbon dioxide

(E) Rubisco’s role in the C-4 process is optimized when oxygen levels are high relative to carbon dioxide levels.
 Opposite

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Jks3000 · Answer

All correct in 13 mins, including 4:30 secs to read..

Raman109 · Answer

4. The author’s reference to “all other atmospheric gases” (Highlighted) plays which one of the following roles in the passage?

(A) It indicates why certain atmospheric conditions can cause excess oxygen to build up and thus hinder photosynthesis in non-C-4 plants as described in the previous paragraph. - "non-C-4 plants" are out of scope.

(B) It supports the claim advanced earlier in the paragraph that oxygen is not the only atmospheric gas whose presence in the leaf can interfere with photosynthesis. - Broadly, this is correct; however, there is no claim as such. Saying it is a claim is hyperbolic. Wrong.

(C) It supports the conclusion that non-C-4 photosynthesis makes use of several atmospheric gases that C-4 photosynthesis does not use. - non-C-4 plants

(D) It explains why carbon dioxide molecules undergo the transformations described later in the paragraph before participating in photosynthesis in C-4 plants. - Ok. Carbon as a gas can't enter as all other gases are blocked; thus, carbon dioxide has to undergo transformations to enter and then release CO2 once it is inside for sugar production.

(E) It advances a broader claim that oxygen levels remain constant in C-4 plants in spite of changes in atmospheric conditions. - "oxygen levels remain constant" is out of scope.

VerbalBot · Answer

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Every culture that has adopted the cultivation of maize—also known as

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Every culture that has adopted the cultivation of maize—also known as

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