Two relatively recent independent developments stand behind the curren

Question

Kudos  for the right answer and explanation
 Very Hard

Two relatively recent independent developments stand behind the current major research effort on nitrogen fixation, the process by which bacteria symbiotically render leguminous plants independent of nitrogen fertilizer. The one development has been the rapid, sustained increase in the price of nitrogen fertilizer. The other development has been the rapid growth of knowledge of and technical sophistication in genetic engineering. Fertilizer prices, largely tied to the price of natural gas, huge amounts of which go into the manufacture of fertilizer, will continue to represent an enormous and escalating economic burden on modern agriculture, spurring the search for alternatives to synthetic fertilizers. And genetic engineering is just the sort of fundamental breakthrough that opens up prospects of wholly novel alternatives. One such novel idea is that of inserting into the chromosomes of plants discrete genes that are not a part of the plants' natural constitution: specifically, the idea of inserting into nonleguminous plants the genes if they can be identified and isolated, that fit the leguminous plants to be hosts for nitrogen-fixing bacteria. Hence, intensified research on legumes.

Nitrogen fixation is a process in which certain bacteria use atmospheric nitrogen gas, which green plants cannot directly utilize, to produce ammonia, a nitrogen compound plants can use.  It is one of nature's great ironies that the availability of nitrogen in the soil frequently sets an upper limit on plant growth even though the plants' leave are bathed in a sea of nitrogen gas . The leguminous plants - among them crop plants such as soybeans, peas, alfalfa, and clover - have solved the nitrogen supply problem by entering into a symbiotic relationship with the bacterial genus Rhizobium; as a matter of fact, there is a specific strain of Rhizobium for each species of legume. The host plant supplies the bacteria with food and protected habitat and receives surplus ammonia in exchange. Hence, legumes can thrive in nitrogen-depleted soil.

Unfortunately, most of the major food crops - including maize, wheat, rice, and potatoes - cannot. On the contrary, many of the high-yielding hybrid varieties of these food crops bred during the Green Revolution of the 1960's were selected specifically to give high yields in response to generous applications of nitrogen fertilizer. This poses an additional, formidable challenge to plant geneticists: they must work on enhancing fixation within the existing symbioses. Unless they succeed, the yield gains of the Green Revolution will be largely lost even if the genes in legumes that equip those plants to enter into a symbiosis with nitrogen fixers are identified and isolated, and even if the transfer of those gene complexes, once they are found, becomes possible. The overall task looks forbidding, but the stakes are too high not to undertake it.    1 1. The primary purpose of the passage is to

(A) expose the fragile nature of the foundations on which the high yields of modern agriculture rest
(B) argue that genetic engineering promises to lead to even higher yields than are achievable with synthetic fertilizers
(C) argue that the capacity for nitrogen-fixing symbioses is transferable to nonleguminous plants
(D) explain the reasons for and the objectives of current research on nitrogen-fixing symbioses
(E) describe the nature of the genes that regulate the symbiosis between legumes and certain bacteria

2 
 
2. According to the passage, there is currently no strain of Rhizobium that can enter into a symbiosis with

(A) alfalfa 
(B) clover 
(C) maize
(D) peas 
(E) soybeans

3

3. The passage implies that which of the following is true of the bacterial genus Rhizobium?

(A) Rhizobium bacteria are found primarily in nitrogen-depleted soils.
(B) Some strains of Rhizobium are not capable of entering into a symbiosis with any plant.
(C) Newly bred varieties of legumes cannot be hosts to any strain of Rhizobium.
(D) Rhizobium bacteria cannot survive outside the protected habitat provided by host plants.
(E) Rhizobium bacteria produce some ammonia for their own purposes.

4 
 
4. It can be inferred from the passage that which of the following was the most influential factor in bringing about intensified research on nitrogen fixation?

(A) The high yields of the Green Revolution 
(B) The persistent upward surge in natural gas prices 
(C) The variety of Rhizobium strains 
(D) The mechanization of modern agriculture 
(E) The environmental ill effects of synthetic fertilizers

5

5. Which of the following situations is most closely analogous to the  situation described  by the author as one of nature's great ironies?

(A) That of a fanner whose crops have failed because the normal midseason rains did not materialize and no preparations for irrigation had been made 
(B) That of a long-distance runner who loses a marathon race because of a wrong turn that cost him twenty seconds 
(C) That of shipwrecked sailors at sea in a lifeboat, with one flask of drinking water to share among them 
(D) That of a motorist who runs out of gas a mere five miles from the nearest gas station . 
(E) That of travelers who want to reach their destination as fast and as cheaply as possible, but find that cost increases as travel speed increases

6

6. According to the passage, the ultimate goal of the current research on nitrogen fixation is to develop

(A) strains of Rhizobium that can enter into symbioses with existing varieties of wheat,rice, and other nonlegumes 
(B) strains of Rhizobium that produce more ammonia for leguminous host plants than do any of the strains presently known 
(C) varieties of wheat, rice, and other nonlegumes that yield as much as do existing varieties, but require less nitrogen 
(D) varieties of wheat, rice, and other nonlegumes that maintain an adequate symbiotic relationship with nitrogen-fixing bacteria and produce high yields 
(E) high-yielding varieties of wheat, rice, and other nonlegumes that are genetically equipped to fix nitrogen from the air without the aid of bacteria

7

7. The author regards the research program under discussion as

(A) original and extensive but ill-defined as to method 
(B) necessary and ambitious but vulnerable to failure 
(C) cogent and worthwhile but severely underfunded 
(D) prohibitively expensive but conceptually elegant 
(E) theoretically fascinating but practically useless

8

8. Most nearly parallel, in its fundamental approach, to the research program described in the passage would be a program designed to

(A) achieve greater frost resistance in frost-tender food plants by means of selective breeding, thereby expanding those plants' area of cultivation 
(B) achieve greater yields from food plants by interplanting crop plants that are mutually beneficial 
(C) find inexpensive and abundant natural substances that could, without reducing yields, be substituted for expensive synthetic fertilizers 
(D) change the genetic makeup of food plants that cannot live in water with high salinity, using genes from plants adapted to saltwater 
(E) develop, through genetic engineering, a genetic configuration for the major food plants that improve the storage characteristics of the edible portion of the plants

auradediligodo · Accepted Answer

Hi everyone,
Got 7/8 correct here.

--------------------------------------------------------------------------------

P1

The author starts with presenting 2 developments related to nitrogen fixation. Then the author proceeds by describing the 2 elements (increase in price for nitrogen fertilizer and genetic engineering) and in the end she gives a couple of examples of what genetic engineering could do.

Purpose:  To present and describe 2 developments related to nitrogen fixation with some examples

P2

Here the author describes more in detail nitrogen fixation and it explains that plants' growth is dependent on the quantity of nitrogen present in the soil. Plus it is mentioned that it is ironic that the abundant quantity of nitrogen present in the air cannot be used. then the author proceeds by presenting a category of plant that found a solution to the nitrogen problem. Such plants establish a relationship with the enzyme R, an enzyme that produces ammonia and that can give some to the plants.

Purpose:  The purpose of this paragraph is to explain what nitrogen fixation is, to highlight a problem related to it and to give a example of a category of plant that overcame such problem.

P3

In the last paragraph we are given that most of the plants are not able to overcome the problem in the same way as the plants discussed in the previous paragraph. Then the author proceeds by mentioning the great gains that such plants had in the past because of the fertilizers and that scientists must find a way to enhance the current symbiotic relationships in order not to loose such gains. Lastly the author claims that such task seems almost impossible but that it is worth trying.

Purpose:  The purpose of this paragraph is to claim that the majority of plants cannot overcome the problem previously mentioned and that scientists must face a difficult but worthy challenge in trying to enhance the current Relationships in such plants.

Main point

The purpose of this passage is to consider possible solutions to the nitrogen fixation problems, starting from two recent developments.

--------------------------------------------------------------------------------

1. The primary purpose of the passage is to

Pre-thinking

Main point question

The purpose of this passage is to consider possible solutions to the nitrogen fixation problems, starting from two recent developments.

(A) expose the fragile nature of the foundations on which the high yields of modern agriculture rest
 Not in line with pre-thinking

(B) argue that genetic engineering promises to lead to even higher yields than are achievable with synthetic fertilizers
 Not in line with pre-thinking

(C) argue that the capacity for nitrogen-fixing symbioses is transferable to nonleguminous plants
 Not in line with pre-thinking

(D)   explain the reasons for and the objectives of current research on nitrogen-fixing symbioses
 in line with pre-thinking

(E) describe the nature of the genes that regulate the symbiosis between legumes and certain bacteria
 Not in line with pre-thinking

--------------------------------------------------------------------------------

2.  According to the passage,  there is currently no strain of Rhizobium that can enter into a symbiosis with

Pre-thinking

Detail question

From last paragraph:" Unfortunately, most of the major food crops - including maize, wheat, rice, and potatoes - cannot.  "

(A) alfalfa 
 Incorrect

(B) clover 
 Incorrect

(C) maize
 In line with pre-thinking

(D) peas 
 Incorrect

(E) soybeans 
 Incorrect

--------------------------------------------------------------------------------

3. The passage implies that which of the following is true of the bacterial genus Rhizobium?

Pre-thinking

Assumption question

Here is the portion of P2 where Rhizobium is mentioned:" with the bacterial genus Rhizobium; as a matter of fact, there is a specific strain of Rhizobium for each species of legume. The host plant supplies the bacteria with food and protected habitat and receives  surplus ammonia  in exchange.  "

(A) Rhizobium bacteria are found primarily in nitrogen-depleted soils.
 Not a must be true statement

(B) Some strains of Rhizobium are not capable of entering into a symbiosis with  any  plant.
 Too extreme and not a must be true statement

(C) Newly bred varieties of legumes cannot be hosts to any strain of Rhizobium.
 Not a must be true statement

(D) Rhizobium bacteria cannot survive outside the protected habitat provided by host plants.
 Not a must be true statement

(E) Rhizobium bacteria produce some ammonia for their own purposes.
 Yes, the author mentions that the bacteria R gives to the hot plant the   surplus  of the ammonia produced. Hence the argument is assuming that the bacteria produces ammonia for other purposes

--------------------------------------------------------------------------------

4. It can be inferred from the passage that which of the following was the most influential factor in bringing about intensified research on nitrogen fixation?

Pre-thinking

Inference question

From the first paragraph:  "The one development has been the rapid, sustained increase in the price of nitrogen fertilizer."

And

"Fertilizer prices, largely tied to the price of natural gas, "

(A) The high yields of the Green Revolution 
 Irrelevant

(B)   The persistent upward surge in natural gas prices 
 Since fertilizers' prices are relate to the gas prices, we can infer that while the gas prices increase also the fertilizers prices increase

(C) The variety of Rhizobium strains 
 Irrelevant

(D) The mechanization of modern agriculture 
 Irrelevant

(E) The environmental ill effects of synthetic fertilizers
 Irrelevant

--------------------------------------------------------------------------------

5. Which of the following situations is most closely analogous to the situation described by the author as one of nature's great ironies?

Pre-thinking

Analogous statement question

Here is the situation from P2: "  It is one of nature's great ironies that the availability of nitrogen in the soil frequently sets an upper limit on plant growth even though the plants' leave are bathed in a sea of nitrogen gas.  ".

Basically we have an object (the plant) that needs a certain element to thrive (nitrogen) but that is surrounded by tons of a similar element that cannot be used and that at the same time has little of the useful element to use (nitrogen in the soil).

(A) That of a fanner whose crops have failed because the normal midseason rains did not materialize and no preparations for irrigation had been made 
 Not in line with pre-thinking

(B) That of a long-distance runner who loses a marathon race because of a wrong turn that cost him twenty seconds 
 Not in line with pre-thinking

(C) That of shipwrecked sailors at sea in a lifeboat, with one flask of drinking water to share among them 
 correct. Sailors have tons of water that cannot be drunk but little of water that they can actually drink.

(D) That of a motorist who runs out of gas a mere five miles from the nearest gas station . 
  Not in line with pre-thinking

(E) That of travelers who want to reach their destination as fast and as cheaply as possible, but find that cost increases as travel speed increases
 Not in line with pre-thinking

--------------------------------------------------------------------------------

6. According to the passage, the ultimate goal of the current research on nitrogen fixation is to develop

Pre-thinking

Detail question

From last paragraph: "  they must work on enhancing fixation within the existing symbioses.  "

(A) strains of Rhizobium that can enter into symbioses with existing varieties of wheat,rice, and other nonlegumes 
 Not in line with pre-thinking

(B) strains of Rhizobium that produce more ammonia for leguminous host plants than do any of the strains presently known 
 Not in line with pre-thinking

(C) varieties of wheat, rice, and other nonlegumes that yield as much as do existing varieties, but require less nitrogen 
 Not in line with pre-thinking

(D)   varieties of wheat, rice, and other nonlegumes that maintain an adequate symbiotic relationship with nitrogen-fixing bacteria and produce high yields 
 Correct

(E) high-yielding varieties of wheat, rice, and other nonlegumes that are genetically equipped to fix nitrogen from the air without the aid of bacteria 
 Not in line with pre-thinking

--------------------------------------------------------------------------------

. The author regards the research program under discussion as

Pre-thinking

Inference question

From last paragraph: " The overall task looks forbidding, but the stakes are too high not to undertake it. "

(A)  original  and extensive but  ill-defined  as to method 
 Incorrect

(B) necessary and ambitious but vulnerable to failure 
 In line with pre-thinking

(C)  cogent and worthwhile but severely underfunded  
 Incorrect

(D) prohibitively  expensive  but conceptually  elegant  
 Incorrect

(E)  theoretically fascinating but practically useless  
 Incorrect

--------------------------------------------------------------------------------

8. Most nearly parallel, in its fundamental approach, to the research program described in the passage would be a program designed to

Pre-thinking

Parallel situation question

Basically we are asked to find a program that aims at strengthening one feature already existing in an object to increase the yields of such object

(A) achieve greater frost resistance in frost-tender food plants by means of selective breeding, thereby expanding those plants' area of cultivation 
 The passage does not aim at expanding the area of cultivation

(B) achieve greater yields from food plants by interplanting crop plants that are mutually beneficial 
 Inconsistent

(C) find inexpensive and abundant natural substances that could, without reducing yields, be substituted for expensive synthetic fertilizers 
 Inconsistent

(D)   change the genetic makeup of food plants that cannot live in water with high salinity, using genes from plants adapted to saltwater 
 I don't particularly agree with the second part of this answer as in the last paragraph it is mentioned that scientists must work on the existing symbioses

(E) develop, through genetic engineering, a genetic configuration for the major food plants that improve the storage characteristics of the edible portion of the plants
 Inconsistent

--------------------------------------------------------------------------------

It is a great day to be alive!

Skywalker18 · Answer

All correct in 14 mins 45 seconds, including 5 mins 30 seconds to read.
Para 1- 2 developments that led to current major research effort on nitrogen fixation- rise in price of nitrogen fertilizer and growth in genetic engineering
Para 2- Nitrogen fixation; the irony; symbiotic relationship between leguminous plants and Rhizobium
Para 3- Unfortunately most of major food crops cannot do symbiosis with R; an additional, formidable challenge to plant geneticists

1. The primary purpose of the passage is to 
(D) explain the reasons for and the objectives of current research on nitrogen-fixing symbioses- Correct, the two reasons are mentioned in first para and the objective is listed in third para.

2. According to the passage, there is currently no strain of Rhizobium that can enter into a symbiosis with 
(C) maize

The leguminous plants - among them crop plants such as soybeans, peas, alfalfa, and clover - have solved the nitrogen supply problem by entering into a symbiotic relationship with the bacterial genus Rhizobium

3. The passage implies that which of the following is true of the bacterial genus Rhizobium? 
(E) Rhizobium bacteria produce some ammonia for their own purposes.- Correct
The host plant supplies the bacteria with food and protected habitat and receives surplus ammonia in exchange. 
 
4. It can be inferred from the passage that which of the following was the most influential factor in bringing about intensified research on nitrogen fixation? 
(B) The persistent upward surge in natural gas prices

The one development has been the rapid, sustained increase in the price of nitrogen fertilizer. 
 Fertilizer prices, largely tied to the price of natural gas, huge amounts of which go into the manufacture of fertilizer, will continue to represent an enormous and escalating economic burden on modern agriculture, spurring the search for alternatives to synthetic fertilizers.

5. Which of the following situations is most closely analogous to the  situation described  by the author as one of nature's great ironies? 
(C) That of shipwrecked sailors at sea in a lifeboat, with one flask of drinking water to share among them - Correct; I am reminded of a line from a poem 'water water everywhere not a drop to drink'

It is one of nature's great ironies that the availability of nitrogen in the soil frequently sets an upper limit on plant growth even though the plants' leave are bathed in a sea of nitrogen gas.

6. According to the passage, the ultimate goal of the current research on nitrogen fixation is to develop

(A) strains of Rhizobium that can enter into symbioses with existing varieties of wheat,rice, and other nonlegumes - incorrect, the bacteria used for fixation need not be Rhizobium
(D) varieties of wheat, rice, and other nonlegumes that maintain an adequate symbiotic relationship with nitrogen-fixing bacteria and produce high yields - Correct, the scientist need to work on varieties of wheat, rice and other nonlegumes and work on enhancing fixation within the existing symbioses

This poses an additional, formidable challenge to plant geneticists: they must work on enhancing fixation within the existing symbioses. Unless they succeed, the yield gains of the Green Revolution will be largely lost even if the genes in legumes that equip those plants to enter into a symbiosis with nitrogen fixers are identified and isolated, and even if the transfer of those gene complexes, once they are found, becomes possible.

7. The author regards the research program under discussion as 
(B) necessary and ambitious but vulnerable to failure - Correct
The overall task looks forbidding, but the stakes are too high not to undertake it.

8. Most nearly parallel, in its fundamental approach, to the research program described in the passage would be a program designed to 
(D) change the genetic makeup of food plants that cannot live in water with high salinity, using genes from plants adapted to saltwater - Correct
plants that live water with high salinity are analogous to leguminous plants with a symbiotic relationship with the bacterial genus Rhizobium

mindsf · Answer

Great explanation for q5. I was looking for an answer saying something like: someone is finding important something that is abundant but can't be taken advantage. Couldn't see through choice C like you, the "sea" there is also water but no one can drink.

QuabityAssurance · Answer

Thank You , Great explanation for question 3 and really a tricky one.

For the last one I chose the intercropping as I kind of felt that mutual benefit idea is somewhat relatable.

Jks3000 · Answer

I doubt the answer for Q3. We cannot infer option E this to be exact. Maybe the bacteria produces it but not for its own use ; Maybe it just produces it as a excreta or left over waste material.

bM22 · Answer

Hi  Jks3000 ,

Lines to refer in the passage: "The host plant supplies the bacteria with food and protected habitat and  receives surplus ammonia  in exchange."

Surplus implies excess of something, after the demand of that particular thing has been met. Thus, Rhizobium bacteria producing  surplus  ammonia would imply that Rhizobium bacteria did use some of ammonia for its own purpose.

Hope This Helps.
Thanks.

VerbalBot · Answer

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Two relatively recent independent developments stand behind the curren

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Two relatively recent independent developments stand behind the curren

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