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It was once assumed that all living things could be divided into...

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It was once assumed that all living things could be divided into... [#permalink]

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The Official Guide for GMAT Review, 10th Edition, 2003

Practice Question
Question No.: RC 183 ~ 189
Page: 378

It was once assumed that all living things could be divided into two fundamental and exhaustive categories. Multicellular plants and animals, as well as many unicellular organisms, are eukaryotic—their large, complex cells have a well-formed nucleus and many organelles. On the other hand, the true bacteria are prokaryotic cell, which are simple and lack a nucleus. The distinction between eukaryotes and bacteria, initially defined in terms of subcellular structures visible with a microscope, was ultimately carried to the molecular level. Here prokaryotic and eukaryotic cells have many features in common. For instance, they translate genetic information into proteins according to the same type of genetic coding. But even where the molecular processes are the same, the details in the two forms are different and characteristic of the respective forms. For example, the amino acid sequences of various enzymes tend to be typically prokaryotic or eukaryotic. The differences between the groups and the similarities within each group made it seem certain to most biologists that the tree of life had only two stems. Moreover, arguments pointing out the extent of both structural and functional differences between eukaryotes and true bacteria convinced many biologists that the precursors of the eukaryotes must have diverged from the common ancestor before the bacteria arose.

Although much of this picture has been sustained by more recent research, it seems fundamentally wrong in one respect. Among the bacteria, there are organisms that are significantly different both from the cells of eukaryotes and from the true bacteria, and it now appears that there are three stems in the tree of life. New techniques for determining the molecular sequence of the RNA of organisms have produced evolutionary information about the degree to which organisms are related, the time since they diverged from a common ancestor, and the reconstruction of ancestral versions of genes. These techniques have strongly suggested that although the true bacteria indeed form a large coherent group, certain other bacteria, the archaebacteria, which are also prokaryotes and which resemble true bacteria, represent a distinct evolutionary branch that far antedates the common ancestor of all true bacteria.

[Reveal] Spoiler:
B

1. The passage is primarily concerned with

(A) detailing the evidence that has led most biologists to replace the trichotomous picture of living organisms with a dichotomous one
(B) outlining the factors that have contributed to the current hypothesis concerning the number of basic categories of living organisms
(C) evaluating experiments that have resulted in proof that the prokaryotes are more ancient than had been expected
(D) summarizing the differences in structure and function found among true bacteria, archaebacteria, and eukaryotes
(E) formulating a hypothesis about the mechanisms of evolution that resulted in the ancestors of the prokaryotes


[Reveal] Spoiler:
C

2. According to the passage, investigations of eukaryotic and prokaryotic cells at the molecular level supported the conclusion that

(A) most eukaryotic organisms are unicellular
(B) complex cells have well-formed nuclei
(C) prokaryotes and eukaryotes form two fundamental categories
(D) subcellular structures are visible with a microscope
(E) prokaryotic and eukaryotic cells have similar enzymes


[Reveal] Spoiler:
E

3. According to the passage, which of the following statements about the two-category hypothesis is likely to be true?

(A) It is promising because it explains the presence of true bacteria-like organisms such as organelles in eukaryotic cells.
(B) It is promising because it explains why eukaryotic cells, unlike prokaryotic cells, tend to form multicellular organisms.
(C) It is flawed because it fails to account for the great variety among eukaryotic organisms.
(D) It is flawed because it fails to account for the similarity between prokaryotes and eukaryotes
(E) It is flawed because it fails to recognize an important distinction among prokaryotes.


[Reveal] Spoiler:
D

4. It can be inferred from the passage that which of the following have recently been compared in order to clarify the fundamental classifications of living things?

(A) The genetic coding in true bacteria and that in other prokaryotes
(B) The organelle structures of archaebacteria, true bacteria, and eukaryotes
(C) The cellular structures of multicellular organisms and unicellular organisms
(D) The molecular sequences in eukaryotic RNA, true bacterial RNA, and archaebacterial RNA
(E) The amino acid sequences in enzymes of various eukaryotic species and those of enzymes in archaebacterial species


[Reveal] Spoiler:
A

5. If the “new techniques” mentioned in line 31 were applied in studies of biological classifications other than bacteria, which of the following is most likely?

(A) Some of those classifications will have to be reevaluated.
(B) Many species of bacteria will be reclassified.
(C) It will be determined that there are four main categories of living things rather than three.
(D) It will be found that true bacteria are much older than eukaryotes
(E) It will be found that there is a common ancestor of the eukaryotes, archaebacteria, and true bacteria.


[Reveal] Spoiler:
C

6. According to the passage, researchers working under the two-category hypothesis were correct in thinking that

(A) prokaryotes form a coherent group
(B) the common ancestor of all living things had complex properties
(C) eukaryotes are fundamentally different from true bacteria
(D) true bacteria are just as complex as eukaryotes
(E) ancestral versions of eukaryotic genes functioned differently from their modern counterparts


[Reveal] Spoiler:
E

7. All of the following statements are supported by the passage EXCEPT:

(A) True bacteria form a distinct evolutionary group.
(B) Archaebacteria are prokaryotes that resemble true bacteria.
(C) True bacteria and eukaryotes employ similar types of genetic coding.
(D) True bacteria and eukaryotes are distinguishable at the subcellular level
(E) Amino acid sequences of enzymes are uniform for eukaryotic and prokaryotic organisms.


[Reveal] Spoiler:
A

8. The author’s attitude toward the view that living things are divided into three categories is best described as one of

(A) tentative acceptance
(B) mild skepticism
(C) limited denial
(D) studious criticism
(E) whole hearted endorsement

[Reveal] Spoiler: Question #1 OA
[Reveal] Spoiler: Question #2 OA
[Reveal] Spoiler: Question #3 OA
[Reveal] Spoiler: Question #4 OA
[Reveal] Spoiler: Question #6 OA
[Reveal] Spoiler: Question #7 OA
[Reveal] Spoiler: Question #8 OA

Last edited by hazelnut on 29 Sep 2017, 23:11, edited 3 times in total.
Edited the question.
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 27 Jun 2008, 16:11
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Notes:
Para 1: Two type of living organism. Muti Cellular: Eukaryotic (Complex Cell and well formed nucleus). True Bacteria:Prokrayotic (lack nucleus). Tree of life had only two stems.

Para 2: Tree of life has 3 stems. Archebachetria far antedates common ancestors of true bacteria.

1. The passage is primarily concerned with
(A) detailing the evidence that has led most biologists to replace the trichotomous picture of living organisms with a dichotomous one
Wrong. Passage says other way round.
(B) outlining the factors that have contributed to the current hypothesis concerning the number of basic categories of living organisms
Correct.

(C) evaluating experiments that have resulted in proof that the prokaryotes are more ancient than had been expected
Wrong. Passage suggest Archebachetria are older than prokaryotes (true bacteria).

(D) summarizing the differences in structure and function found among true bacteria, archaebacteria, and eukaryotes
Wrong. First para discusses “differences in structure and function found among true bacteria, and eukaryotes”. Moreover it is not complete passage in itself.

(E) formulating a hypothesis about the mechanisms of evolution that resulted in the ancestors of the prokaryotes
Wrong. There is no hypothesis formulated. Only result of studies are given.


2. According to the passage, investigations of eukaryotic and prokaryotic cells at the molecular level supported the conclusion that
This is explained in first para. From “Here prokaryotic and eukaryotic cells have
many features in common” to end of the para 1 it is all about molecular similarities and differences.
(A) most eukaryotic organisms are unicellular
Wrong. This is explained initially at start of the para but not with regard to molecular structure.

(B) complex cells have well-formed nuclei
Wrong. This is explained initially at start of the para but not with regard to molecular structure.

(C) prokaryotes and eukaryotes form two fundamental categories
Seems Correct. Para 1 says “The differences between the groups and the similarities within each group made it seem certain to most biologists that the tree of life had only two stems”

(D) subcellular structures are visible with a microscope
Question is asking about “molecular” level so nothing to do with “sub cellular” although this is true. As explained in para 1.

(E) prokaryotic and eukaryotic cells have similar enzymes
Wrong. Para 1 says “the amino acid sequences of various enzymes tend to be typically prokaryotic or eukaryotic” means they are different.


3. According to the passage, which of the following statements about the two-category hypothesis is likely to be true?
Referring notes we see para 1 tells “tree of life” has two stems, but para 2 tells that “tree of life” has 3 stems. So “two-category hypothesis” is not promising, it is flawed.

(A) It is promising because it explains the presence of true bacteria-like organisms such as organelles in eukaryotic cells.
Wrong

(B) It is promising because it explains why eukaryotic cells, unlike prokaryotic cells, tend to form multicellular organisms.
Wrong

(C) It is flawed because it fails to account for the great variety among eukaryotic organisms.
2 category hypotheses is false because there is 3 categories not because earlier hypothesis cannot account for eukaryotic organisms.

(D) It is flawed because it fails to account for the similarity between prokaryotes and eukaryotes
2 category hypotheses is false because there is 3 categories not because it fails to account for similarity. In fact study does says at few instances these two seems similar.

(E) It is flawed because it fails to recognize an important distinction among prokaryotes.
Seems Correct. There is a third divison which is kind of “prokaryotes” but predates it.


4. It can be inferred from the passage that which of the following have recently been compared in order to clarify the fundamental classifications of living things?
Para 2 says “New techniques for determining the molecular sequence of the RNA of organisms”. So most probably it is study of molecular sequences of RNA.
(A) The genetic coding in true bacteria and that in other prokaryotes
Wrong. “True Bacteria” and “prokaryotes” are same thing. But in all possibility study was done of all three structures.

(B) The organelle structures of archaebacteria, true bacteria, and eukaryotes
Hold it. Look promising.

(C) The cellular structures of multicellular organisms and unicellular organisms
Wrong. “Muticelluar” and “unicellular” are Eukaryotes only and we need all the 3 structures.
(D) The molecular sequences in eukaryotic RNA, true bacterial RNA, and archaebacterial RNA
Looks promising. I will drop B and select this as best choice.

(E) The amino acid sequences in enzymes of various eukaryotic species and those of enzymes in archaebacterial species
Wrong. May be true. But new study also concluded about “true bacteria” so I will discount this.


5. If the “new techniques” mentioned in line 31 were applied in studies of biological classifications other than bacteria, which of the following is most likely?
(A) Some of those classifications will have to be reevaluated.
Seems OK. As study of bacteria revealed different classification so there are chances that study of other life form may also yield similar support.

(B) Many species of bacteria will be reclassified.
It classified bacteria into 2 class not into many species. Moreover question is asking about “biological classifications other than bacteria” not on bacteria.

(C) It will be determined that there are four main categories of living things rather than three.
Wrong. May be true, may be not. Not supported. Moreover question is asking about “biological classifications other than bacteria” not on bacteria.

(D) It will be found that true bacteria are much older than eukaryotes
Wrong. May be true, may be not. Not supported. Moreover question is asking about “biological classifications other than bacteria” not on bacteria.

(E) It will be found that there is a common ancestor of the eukaryotes, archaebacteria, and true bacteria.
Wrong. May be true, may be not. Not supported. Moreover question is asking about “biological classifications other than bacteria” not on bacteria.


6. According to the passage, researchers working under the two-category hypothesis were correct in thinking that
(A) prokaryotes form a coherent group
Wrong not supported.

(B) the common ancestor of all living things had complex properties
Wrong. Not supported.

(C) eukaryotes are fundamentally different from true bacteria
Seems Correct.

(D) true bacteria are just as complex as eukaryotes
Wrong. Not supported.

(E) ancestral versions of eukaryotic genes functioned differently from their modern counterparts
Wrong. Not supported.


7. All of the following statements are supported by the passage EXCEPT:
(A) True bacteria form a distinct evolutionary group.
True. “there are organisms that are significantly different both from the cells of eukaryotes and from the true bacteria”
(B) Archaebacteria are prokaryotes that resemble true bacteria.
True. “the archae bacteria , which are also prokaryotes and which resemble true bacteria”
(C) True bacteria and eukaryotes employ similar types of genetic coding.
Ture. “RNA of organisms have produced evolutionary information about the degree to which organisms are related”
(D) True bacteria and eukaryotes are distinguishable at the subcellular level
True. “The distinction between eukaryotes and bacteria, initially defined in terms of sub cellular structures visible with a microscope”
(E) Amino acid sequences of enzymes are uniform for eukaryotic and prokaryotic organisms.
False (so correct answer). “the amino acid sequences of various enzymes
tend to be typically prokaryotic or eukaryotic”



8. The author’s attitude toward the view that living things are divided into three categories is best described as one of
Para 2 says “it now appears that there are three stems in the tree of life”. Which inidiates that author is sort of accepting it.
(A) tentative acceptance
Correct.

(B) mild skepticism
Wrong. There is no point which indicates author is skeptic about the claim.

(C) limited denial
Wrong. Author is accepting it and not denying it.

(D) studious criticism
Wrong. Author is accepting it and not criticizing it.

(E) whole hearted endorsement
Wrong. Although author does accept it but no where in passage it suggest that author is very positive about it.

Buddy please post OAs. I would like to confirm my answers.
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 27 Jun 2008, 22:16
Thanks Abhijit,
Amazing explanations! +1 Kudos to you!

The OAs are:

1. B
2. C
3. E
4. D
5. A
6. C
7. E
8. A
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 22 Dec 2012, 09:25
abhijit_sen wrote:
Notes:
Para 1: Two type of living organism. Muti Cellular: Eukaryotic (Complex Cell and well formed nucleus). True Bacteria:Prokrayotic (lack nucleus). Tree of life had only two stems.

Para 2: Tree of life has 3 stems. Archebachetria far antedates common ancestors of true bacteria.

1. The passage is primarily concerned with
(A) detailing the evidence that has led most biologists to replace the trichotomous picture of living organisms with a dichotomous one
Wrong. Passage says other way round.
(B) outlining the factors that have contributed to the current hypothesis concerning the number of basic categories of living organisms
Correct.

(C) evaluating experiments that have resulted in proof that the prokaryotes are more ancient than had been expected
Wrong. Passage suggest Archebachetria are older than prokaryotes (true bacteria).

(D) summarizing the differences in structure and function found among true bacteria, archaebacteria, and eukaryotes
Wrong. First para discusses “differences in structure and function found among true bacteria, and eukaryotes”. Moreover it is not complete passage in itself.

(E) formulating a hypothesis about the mechanisms of evolution that resulted in the ancestors of the prokaryotes
Wrong. There is no hypothesis formulated. Only result of studies are given.


2. According to the passage, investigations of eukaryotic and prokaryotic cells at the molecular level supported the conclusion that
This is explained in first para. From “Here prokaryotic and eukaryotic cells have
many features in common” to end of the para 1 it is all about molecular similarities and differences.
(A) most eukaryotic organisms are unicellular
Wrong. This is explained initially at start of the para but not with regard to molecular structure.

(B) complex cells have well-formed nuclei
Wrong. This is explained initially at start of the para but not with regard to molecular structure.

(C) prokaryotes and eukaryotes form two fundamental categories
Seems Correct. Para 1 says “The differences between the groups and the similarities within each group made it seem certain to most biologists that the tree of life had only two stems”

(D) subcellular structures are visible with a microscope
Question is asking about “molecular” level so nothing to do with “sub cellular” although this is true. As explained in para 1.

(E) prokaryotic and eukaryotic cells have similar enzymes
Wrong. Para 1 says “the amino acid sequences of various enzymes tend to be typically prokaryotic or eukaryotic” means they are different.


3. According to the passage, which of the following statements about the two-category hypothesis is likely to be true?
Referring notes we see para 1 tells “tree of life” has two stems, but para 2 tells that “tree of life” has 3 stems. So “two-category hypothesis” is not promising, it is flawed.

(A) It is promising because it explains the presence of true bacteria-like organisms such as organelles in eukaryotic cells.
Wrong

(B) It is promising because it explains why eukaryotic cells, unlike prokaryotic cells, tend to form multicellular organisms.
Wrong

(C) It is flawed because it fails to account for the great variety among eukaryotic organisms.
2 category hypotheses is false because there is 3 categories not because earlier hypothesis cannot account for eukaryotic organisms.

(D) It is flawed because it fails to account for the similarity between prokaryotes and eukaryotes
2 category hypotheses is false because there is 3 categories not because it fails to account for similarity. In fact study does says at few instances these two seems similar.

(E) It is flawed because it fails to recognize an important distinction among prokaryotes.
Seems Correct. There is a third divison which is kind of “prokaryotes” but predates it.


4. It can be inferred from the passage that which of the following have recently been compared in order to clarify the fundamental classifications of living things?
Para 2 says “New techniques for determining the molecular sequence of the RNA of organisms”. So most probably it is study of molecular sequences of RNA.
(A) The genetic coding in true bacteria and that in other prokaryotes
Wrong. “True Bacteria” and “prokaryotes” are same thing. But in all possibility study was done of all three structures.

(B) The organelle structures of archaebacteria, true bacteria, and eukaryotes
Hold it. Look promising.

(C) The cellular structures of multicellular organisms and unicellular organisms
Wrong. “Muticelluar” and “unicellular” are Eukaryotes only and we need all the 3 structures.
(D) The molecular sequences in eukaryotic RNA, true bacterial RNA, and archaebacterial RNA
Looks promising. I will drop B and select this as best choice.

(E) The amino acid sequences in enzymes of various eukaryotic species and those of enzymes in archaebacterial species
Wrong. May be true. But new study also concluded about “true bacteria” so I will discount this.


5. If the “new techniques” mentioned in line 31 were applied in studies of biological classifications other than bacteria, which of the following is most likely?
(A) Some of those classifications will have to be reevaluated.
Seems OK. As study of bacteria revealed different classification so there are chances that study of other life form may also yield similar support.

(B) Many species of bacteria will be reclassified.
It classified bacteria into 2 class not into many species. Moreover question is asking about “biological classifications other than bacteria” not on bacteria.

(C) It will be determined that there are four main categories of living things rather than three.
Wrong. May be true, may be not. Not supported. Moreover question is asking about “biological classifications other than bacteria” not on bacteria.

(D) It will be found that true bacteria are much older than eukaryotes
Wrong. May be true, may be not. Not supported. Moreover question is asking about “biological classifications other than bacteria” not on bacteria.

(E) It will be found that there is a common ancestor of the eukaryotes, archaebacteria, and true bacteria.
Wrong. May be true, may be not. Not supported. Moreover question is asking about “biological classifications other than bacteria” not on bacteria.


6. According to the passage, researchers working under the two-category hypothesis were correct in thinking that
(A) prokaryotes form a coherent group
Wrong not supported.

(B) the common ancestor of all living things had complex properties
Wrong. Not supported.

(C) eukaryotes are fundamentally different from true bacteria
Seems Correct.

(D) true bacteria are just as complex as eukaryotes
Wrong. Not supported.

(E) ancestral versions of eukaryotic genes functioned differently from their modern counterparts
Wrong. Not supported.


7. All of the following statements are supported by the passage EXCEPT:
(A) True bacteria form a distinct evolutionary group.
True. “there are organisms that are significantly different both from the cells of eukaryotes and from the true bacteria”
(B) Archaebacteria are prokaryotes that resemble true bacteria.
True. “the archae bacteria , which are also prokaryotes and which resemble true bacteria”
(C) True bacteria and eukaryotes employ similar types of genetic coding.
Ture. “RNA of organisms have produced evolutionary information about the degree to which organisms are related”
(D) True bacteria and eukaryotes are distinguishable at the subcellular level
True. “The distinction between eukaryotes and bacteria, initially defined in terms of sub cellular structures visible with a microscope”
(E) Amino acid sequences of enzymes are uniform for eukaryotic and prokaryotic organisms.
False (so correct answer). “the amino acid sequences of various enzymes
tend to be typically prokaryotic or eukaryotic”



8. The author’s attitude toward the view that living things are divided into three categories is best described as one of
Para 2 says “it now appears that there are three stems in the tree of life”. Which inidiates that author is sort of accepting it.
(A) tentative acceptance
Correct.

(B) mild skepticism
Wrong. There is no point which indicates author is skeptic about the claim.

(C) limited denial
Wrong. Author is accepting it and not denying it.

(D) studious criticism
Wrong. Author is accepting it and not criticizing it.

(E) whole hearted endorsement
Wrong. Although author does accept it but no where in passage it suggest that author is very positive about it.

Buddy please post OAs. I would like to confirm my answers.






Dude its awesome thanks so much. I need to clarify one thing in question 7. Is E wrong just because it did not use the term "various". And since it did not use that term is that sentence mean all of the enzymes??
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 09 Aug 2016, 05:46
\sqrt{}1. The passage is primarily concerned with

A) detailing the evidence that has led most biologists to replace the trichotomous picture of living organisms with a dichotomous one
B) outlining the factors that have contributed to the current hypothesis concerning the number of basic categories of living organisms
C) evaluating experiments that have resulted in proof that the prokaryotes are more ancient than had been expected
D) summarizing the differences in structure and function found among true bacteria, archaebacteria, and eukaryotes
E) formulating a hypothesis about the mechanisms of evolution that resulted in the ancestors of the prokaryotes

abhijit_sen: I do not agree with the reason why you discard option C.

"Wrong. Passage suggest Archebachetria are older than prokaryotes (true bacteria)."

The passage states "the archaebacteria, which are also prokaryotes…”. Instead, I would rather discard it because the option says that "experiments that have resulted in proof that...", while the text states that "These techniques have strongly suggested that...".
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 09 Aug 2016, 05:50
Quote:
It was once assumed that all living things could be divided into two fundamental and exhaustive categories. Multicellular plants and animals, as well as many unicellular organisms, are eukaryotic—their large, complex cells have a well-formed nucleus and many organelles. On the other hand, the true bacteria are prokaryotic cell, which are simple and lack a nucleus. The distinction between eukaryotes and bacteria, initially defined in terms of subcellular structures visible with a microscope, was ultimately carried to the molecular level. Here prokaryotic and eukaryotic cells have many features in common. For instance, they translate genetic information into proteins according to the same type of genetic coding. But even where the molecular processes are the same, the details in the two forms are different and characteristic of the respective forms. For example, the amino acid sequences of various enzymes tend to be typically prokaryotic or eukaryotic. The differences between the groups and the similarities within each group made it seem certain to most biologists that the tree of life had only two stems. Moreover, arguments pointing out the extent of both structural and functional differences between eukaryotes and true bacteria convinced many biologists that the precursors of the eukaryotes must have diverged from the common ancestor before the bacteria arose.

Although much of this picture has been sustained by more recent research, it seems fundamentally wrong in one respect. Among the bacteria, there are organisms that are significantly different both from the cells of eukaryotes and from the true bacteria, and it now appears that there are three stems in the tree of life. New techniques for determining the molecular sequence of the RNA of organisms have produced evolutionary information about the degree to which organisms are related, the time since they diverged from a common ancestor, and the reconstruction of ancestral versions of genes. These techniques have strongly suggested that although the true bacteria indeed form a large coherent group, certain other bacteria, the archaebacteria, which are also prokaryotes and which resemble true bacteria, represent a distinct evolutionary branch that far antedates the common ancestor of all true bacteria.

1. The passage is primarily concerned with

A) detailing the evidence that has led most biologists to replace the trichotomous picture of living organisms with a dichotomous one
B) outlining the factors that have contributed to the current hypothesis concerning the number of basic categories of living organisms
C) evaluating experiments that have resulted in proof that the prokaryotes are more ancient than had been expected
D) summarizing the differences in structure and function found among true bacteria, archaebacteria, and eukaryotes
E) formulating a hypothesis about the mechanisms of evolution that resulted in the ancestors of the prokaryotes

Last edited by hazelnut on 29 Sep 2017, 23:09, edited 1 time in total.
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 09 Aug 2016, 05:53
OA is B.

I can find a reason to discard the remaining options. However, I do not see how does the passage "outline the factors that have contributed to the current hypothesis...".
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 13 Aug 2016, 06:36
EBITDA wrote:
OA is B.

I can find a reason to discard the remaining options. However, I do not see how does the passage "outline the factors that have contributed to the current hypothesis...".


Initially in the passage, author talks about only the two stems of the tree of life. It says there has been some similarities found at the molecular level but inspite of that they are more or less categorized as two stems only.

2nd paragraph initially talks about the similar division but then it provides the exception to this division and provided several techniques that have proved the existence of the third division. hence, here I believe by factors, author mean the various techniques that have contributed to make us believe that there are actually three divisions.

Can you please add the other questions of this passage as well?
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 29 Sep 2017, 23:46
gmatcrook wrote:
The Official Guide for GMAT Review, 10th Edition, 2003

Practice Question
Question No.: RC 183 ~ 189
Page: 378

It was once assumed that all living things could be divided into two fundamental and exhaustive categories. Multicellular plants and animals, as well as many unicellular organisms, are eukaryotic—their large, complex cells have a well-formed nucleus and many organelles. On the other hand, the true bacteria are prokaryotic cell, which are simple and lack a nucleus. The distinction between eukaryotes and bacteria, initially defined in terms of subcellular structures visible with a microscope, was ultimately carried to the molecular level. Here prokaryotic and eukaryotic cells have many features in common. For instance, they translate genetic information into proteins according to the same type of genetic coding. But even where the molecular processes are the same, the details in the two forms are different and characteristic of the respective forms. For example, the amino acid sequences of various enzymes tend to be typically prokaryotic or eukaryotic. The differences between the groups and the similarities within each group made it seem certain to most biologists that the tree of life had only two stems. Moreover, arguments pointing out the extent of both structural and functional differences between eukaryotes and true bacteria convinced many biologists that the precursors of the eukaryotes must have diverged from the common ancestor before the bacteria arose.

Although much of this picture has been sustained by more recent research, it seems fundamentally wrong in one respect. Among the bacteria, there are organisms that are significantly different both from the cells of eukaryotes and from the true bacteria, and it now appears that there are three stems in the tree of life. New techniques for determining the molecular sequence of the RNA of organisms have produced evolutionary information about the degree to which organisms are related, the time since they diverged from a common ancestor, and the reconstruction of ancestral versions of genes. These techniques have strongly suggested that although the true bacteria indeed form a large coherent group, certain other bacteria, the archaebacteria, which are also prokaryotes and which resemble true bacteria, represent a distinct evolutionary branch that far antedates the common ancestor of all true bacteria.
4. It can be inferred from the passage that which of the following have recently been compared in order to clarify the fundamental classifications of living things?

(A) The genetic coding in true bacteria and that in other prokaryotes
(B) The organelle structures of archaebacteria, true bacteria, and eukaryotes
(C) The cellular structures of multicellular organisms and unicellular organisms
(D) The molecular sequences in eukaryotic RNA, true bacterial RNA, and archaebacterial RNA
(E) The amino acid sequences in enzymes of various eukaryotic species and those of enzymes in archaebacterial species



"New techniques for determining the molecular sequence of the RNA of organisms have produced evolutionary information about the degree to which organisms are related, the time since they diverged from a common ancestor, and the reconstruction of ancestral versions of genes."

Answer = D
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 27 Oct 2017, 06:14
I did the 4th question wrong. Please explain why (A) is wrong and (D) correct. The information regarding this question is present in the last few lines of the passage. There has been mention of true bacteria and the new type of bacteria, but there hasn't been any discussion of eukaryotes. Also the method discussed involves "reconstruction of genes". This made me choose (A) over (D), even when D has the keyword "RNA" in it, the passage hasn't mentioned eukaryotes in the lines describing the comparison. Please help. Am I making a strategic mistake? Is my approach wrong here? Please help
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Re: It was once assumed that all living things could be divided into... [#permalink]

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New post 05 Nov 2017, 22:24
Quote:
4. It can be inferred from the passage that which of the following have recently been compared in order to clarify the fundamental classifications of living things?

(A) The genetic coding in true bacteria and that in other prokaryotes
(B) The organelle structures of archaebacteria, true bacteria, and eukaryotes
(C) The cellular structures of multicellular organisms and unicellular organisms
(D) The molecular sequences in eukaryotic RNA, true bacterial RNA, and archaebacterial RNA
(E) The amino acid sequences in enzymes of various eukaryotic species and those of enzymes in archaebacterial species

ShashankDave wrote:
I did the 4th question wrong. Please explain why (A) is wrong and (D) correct. The information regarding this question is present in the last few lines of the passage. There has been mention of true bacteria and the new type of bacteria, but there hasn't been any discussion of eukaryotes. Also the method discussed involves "reconstruction of genes". This made me choose (A) over (D), even when D has the keyword "RNA" in it, the passage hasn't mentioned eukaryotes in the lines describing the comparison. Please help. Am I making a strategic mistake? Is my approach wrong here? Please help

The recent research is discussed in the second paragraph. This research has suggested that "among the bacteria, there are organisms that are significantly different both from the cells of eukaryotes and from the true bacteria, and it now appears that there are three stems in the tree of life." This portion suggests that the recent research compared eukaryotes, true bacteria, and a third type of life (which is later identified as archaebacteria).

We are then told that "new techniques for determining the molecular sequence of the RNA of organisms have produced evolutionary information about..." So we are first told that recent research has led to a distinction between three types of life. We are then told that this recent research involved examining the molecular sequences of organisms' RNA. Thus, we can INFER that the recent research involved comparing the "molecular sequences in eukaryotic RNA, true bacterial RNA, and archaebacterial RNA" - choice (D).

As for choice (A), we are told in the first paragraph that "{at the molecular level} prokaryotic and eukaryotic cells have many features in common. For instance, they translate genetic information into proteins according to the same type of genetic coding". So if we were to compare the genetic coding of the prokaryotic and eukaryotic cells, we would find similarities, not differences. Unlike the recent research, comparing the genetic coding would NOT suggest that we need to further divide up the tree of life. Thus, choice (A) likely does not apply to the recent research.

So (D) is the best answer.
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Re: It was once assumed that all living things could be divided into...   [#permalink] 05 Nov 2017, 22:24
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