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555-605 (Medium)|   Long Passage|   Science|                     
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Until recently, scientists did not know of a close vertebrate analogue 01 May 2022, 10:42
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Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees, whereby individuals cooperate, sometimes even sacrificing their own opportunities to survive and reproduce, for the good of others. However, such a vertebrate society may exist among underground colonies of the highly social rodent Heterocephalus glaber, the naked mole rat.

A naked mole rat colony, like a beehive, wasp's nest, or termite mound, is ruled by its queen, or reproducing female. Other adult female mole rats neither ovulate nor breed. The queen is the largest member of the colony, and she maintains her breeding status through a mixture of behavioral and, presumably, chemical control. Queens have been long-lived in captivity, and when they die or are removed from a colony one sees violent fighting for breeding status among the larger remaining females, leading to a takeover by a new queen.

Eusocial insect societies have rigid caste systems, each insect's role being defined by its behavior, body shape, and physiology. In naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status (reproduction being limited to the queen and a few males), body size, and perhaps age. Smaller non-breeding members, both male and female, seem to participate primarily in gathering food, transporting nest material, and tunneling. Larger nonbreeders are active in defending the colony and perhaps in removing dirt from the tunnels. Jarvis' work has suggested that differences in growth rates may influence the length of time that an individual performs a task, regardless of its age.

Cooperative breeding has evolved many times in vertebrates, but unlike naked mole rats, most cooperatively breeding vertebrates (except the wild dog, Lycaon pictus) are dominated by a pair of breeders rather than by a single breeding female. The division of labor within social groups is less pronounced among other vertebrates than among naked mole rats, colony size is much smaller, and mating by subordinate females may not be totally suppressed, whereas in naked mole rat colonies subordinate females are not sexually active, and many never breed.
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Hi avigutman GMATNinja IanStewart

This is an interesting passage, but I have some questions that no previous post in this thread has discussed yet, so I decided to write my post and hope you could share some thoughts when you have time. :)

(By the way, this passage made me curious what these special rats are, and it is really hard to tell from these rats' appearance that they are altruistic--they look special and even a bit aggressive.)

Quote:

3. It can be inferred from the passage that the performance of tasks in naked mole rat colonies differs from task performance in eusocial insect societies in which of the following ways?

(A) In naked mole rat colonies, all tasks are performed cooperatively.
(B) In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape.
(C) In naked mole rat colonies, breeding is limited to the largest animals.
(D) In eusocial insect societies, reproduction is limited to a single female.
(E) In eusocial insect societies, the distribution of tasks is based on body size.
Show more

This is an inference question mainly relevant to the second and third paragraph, which talk about the similarities and difference between the eusocial insects and the naked mole rats. I would like to check all the five options, but first I hope to compare the option (B) and (E).

Quote:

(B) In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape.
(E) In eusocial insect societies, the distribution of tasks is based on body size.
Show more

I can see why the option (E) is incorrect. Although the paragraph does not explicitly say that the eusocial insects distribute their jobs by the body size, it says that each insect's role is defined by the body shape and it could be inferred that an individual's role in the community is related to the job it does. Because body shape also affects job distribution among rats--larger rats do some jobs and smaller rats do other jobs--the option (E) is gone.

But I am not sure about the option (B), which is the correct answer: "In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape."

Some members said that this could be inferred from "each insect's role being defined by its behavior, body shape, and physiology. In naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status (reproduction being limited to the queen and a few males), body size, and perhaps age." But I am not fully convinced for two reasons:

1. Does the adverb "primarily" modify only the first noun "reproductive status?" Or, does it modify all the three following nouns?
If it modifies all the three nouns, then body size also plays a primary role in the difference in behavior among rats. I do not think that it is strange for the author to use the adverb "primarily" to modify three nouns at the same time, because he or she might want to express the idea that these three factors are the most primary factors among all factors.

2. The third paragraph talks much about how larger rats do some jobs and smaller rats do other jobs. It seems to me that these descriptions suggest that a rat's body shape affects what kind of jobs it does. Cannot we infer from this information that the body shape plays an important role in the distribution of task in the rat societies?

In eusocial insect societies, each insect's role is defined by three factors including the body shape. And in the rate societies, the body shape also plays an important role. I cannot understand how we can infer that "In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape."

Meanwhile, I noticed that in the third paragraph, there is an idiom "on the other hand," which usually suggests whatever comes is to say something different from the preceding message. I tried to use this idiom to help myself understand the difference between the eusocial insects and rats, but to no avail. To be very frank, I am even a bit confused why the author uses this idiom, because the part following "on the other hand" does not really seem very different from the preceding part.

Eusocial insect societies have rigid caste systems, each insect's role being defined by its behavior, body shape, and physiology. In naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status (reproduction being limited to the queen and a few males), body size, and perhaps age.

The first part talks about the insects' role, and behavior is one of the three factors deciding the role. The second part, following "on the other hand," talks about the difference in rats' behavior. I think they are more like two separate topics. It would make more sense to me if the author wrote "each insect's role is defined by three factors, and on the other hand, each rat's role is decided by other factors." I am not saying that the "parallelism"/"comparison" concept in the SC section should be applied here, but it just puzzled me whether the idiom "on the other hand" gives us some valuable hints.

I would also like to check the option (C) and (D):

Quote:

(C) In naked mole rat colonies, breeding is limited to the largest animals.
(D) In eusocial insect societies, reproduction is limited to a single female.
Show more

I think these two options are relevant to the second paragraph (cited below). May I confirm whether we can eliminate the option (D) with the sentence that is colored in orange? And, does the description of the queen, colored in blue, apply only to the rat queen or to both queens of the rat societies and the eusocial insects societies?

A naked mole rat colony, like a beehive, wasp's nest, or termite mound, is ruled by its queen, or reproducing female. Other adult female mole rats neither ovulate nor breed. The queen is the largest member of the colony, and she maintains her breeding status through a mixture of behavioral and, presumably, chemical control. Queens have been long-lived in captivity, and when they die or are removed from a colony one sees violent fighting for breeding status among the larger remaining females, leading to a takeover by a new queen.

At my first read, I thought that the queen only refers to the rat queen. But for my second read, I noticed that the parts describing the queen do not really limit themselves to the scope of the rat societies. Since this paragraph mainly talks about the similarities between the eusocial insects and the rats, I wonder whether these descriptions also apply to the insect queen. This paragraph might be less meaningful if the properties (being the largest member, fighting among other adult female when the queen dies, and so on) are only those of the rat queen, but would still work.

I might be doing more analyses than necessary here, because whether the queen descriptions refers to only the rat queen, we can eliminate the option (C), just for different reasons. But I hope to know how you would understand the queen part in the second paragraph--I feel that I might be able to improve my grasp on reading structure with this.

For the last option (A):
Quote:

(A) In naked mole rat colonies, all tasks are performed cooperatively.
Show more


I hope to confirm whether the use of "all" is the main reason the option (A) is gone. From the second and third paragraphs, we can know that both the eusocial insects and the rats perform the tasks cooperatively, but we just do not know the comparative extent of their cooperation, do we?


Sorry that my question is a bit long.
Thank you for your thoughts and insights. :)
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Until recently, scientists did not know of a close vertebrate analogue 02 May 2022, 13:45
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Quote:

3. It can be inferred from the passage that the performance of tasks in naked mole rat colonies differs from task performance in eusocial insect societies in which of the following ways?

(A) In naked mole rat colonies, all tasks are performed cooperatively.
(B) In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape.
(C) In naked mole rat colonies, breeding is limited to the largest animals.
(D) In eusocial insect societies, reproduction is limited to a single female.
(E) In eusocial insect societies, the distribution of tasks is based on body size.

I am not sure about the option (B), which is the correct answer: "In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape."

Some members said that this could be inferred from "each insect's role being defined by its behavior, body shape, and physiology. In naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status (reproduction being limited to the queen and a few males), body size, and perhaps age." But I am not fully convinced for two reasons:

1. Does the adverb "primarily" modify only the first noun "reproductive status?" Or, does it modify all the three following nouns?
If it modifies all the three nouns, then body size also plays a primary role in the difference in behavior among rats. I do not think that it is strange for the author to use the adverb "primarily" to modify three nouns at the same time, because he or she might want to express the idea that these three factors are the most primary factors among all factors.
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I completely agree with you, GraceSCKao. The reason I chose B is because there's a huge difference (in my opinion) between "body shape" and "body size."

GraceSCKao
2. The third paragraph talks much about how larger rats do some jobs and smaller rats do other jobs. It seems to me that these descriptions suggest that a rat's body shape affects what kind of jobs it does. Cannot we infer from this information that the body shape plays an important role in the distribution of task in the rat societies?

In eusocial insect societies, each insect's role is defined by three factors including the body shape. And in the rat societies, the body shape also plays an important role. I cannot understand how we can infer that "In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape."

Meanwhile, I noticed that in the third paragraph, there is an idiom "on the other hand," which usually suggests whatever comes is to say something different from the preceding message. I tried to use this idiom to help myself understand the difference between the eusocial insects and rats, but to no avail. To be very frank, I am even a bit confused why the author uses this idiom, because the part following "on the other hand" does not really seem very different from the preceding part.

Eusocial insect societies have rigid caste systems, each insect's role being defined by its behavior, body shape, and physiology. In naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status (reproduction being limited to the queen and a few males), body size, and perhaps age.

The first part talks about the insects' role, and behavior is one of the three factors deciding the role. The second part, following "on the other hand," talks about the difference in rats' behavior. I think they are more like two separate topics. It would make more sense to me if the author wrote "each insect's role is defined by three factors, and on the other hand, each rat's role is decided by other factors." I am not saying that the "parallelism"/"comparison" concept in the SC section should be applied here, but it just puzzled me whether the idiom "on the other hand" gives us some valuable hints.
Show more
Does my point above clarify all of that?
GraceSCKao

I would also like to check the option (C) and (D):

Quote:

(C) In naked mole rat colonies, breeding is limited to the largest animals.
(D) In eusocial insect societies, reproduction is limited to a single female.

I think these two options are relevant to the second paragraph (cited below). May I confirm whether we can eliminate the option (D) with the sentence that is colored in orange? And, does the description of the queen, colored in blue, apply only to the rat queen or to both queens of the rat societies and the eusocial insects societies?

A naked mole rat colony, like a beehive, wasp's nest, or termite mound, is ruled by its queen, or reproducing female. Other adult female mole rats neither ovulate nor breed. The queen is the largest member of the colony, and she maintains her breeding status through a mixture of behavioral and, presumably, chemical control. Queens have been long-lived in captivity, and when they die or are removed from a colony one sees violent fighting for breeding status among the larger remaining females, leading to a takeover by a new queen.

At my first read, I thought that the queen only refers to the rat queen. But for my second read, I noticed that the parts describing the queen do not really limit themselves to the scope of the rat societies. Since this paragraph mainly talks about the similarities between the eusocial insects and the rats, I wonder whether these descriptions also apply to the insect queen. This paragraph might be less meaningful if the properties (being the largest member, fighting among other adult female when the queen dies, and so on) are only those of the rat queen, but would still work.

I might be doing more analyses than necessary here, because whether the queen descriptions refers to only the rat queen, we can eliminate the option (C), just for different reasons. But I hope to know how you would understand the queen part in the second paragraph--I feel that I might be able to improve my grasp on reading structure with this.
Show more
My first reaction to this is that it's a terrible idea to look at the second paragraph, because trap answers are likely to play on stuff that you'll see there. Big picture, the second paragraph discusses the similarities, while the third paragraph discusses differences. So, when attempting to solve this particular problem, the more we can confine ourselves to the third paragraph the more likely we are to succeed.
Separately, to answer your question about which queen is discussed in the second paragraph: in my opinion, it's discussing the rat queen (while it's possible that this stuff happens to also be true of insect queens, we have no way of knowing). The reason I say this is because of the preceding sentence: Other adult female mole rats neither ovulate nor breed.
GraceSCKao
For the last option (A):
Quote:

(A) In naked mole rat colonies, all tasks are performed cooperatively.


I hope to confirm whether the use of "all" is the main reason the option (A) is gone. From the second and third paragraphs, we can know that both the eusocial insects and the rats perform the tasks cooperatively, but we just do not know the comparative extent of their cooperation, do we?
Show more
Yes, kind of. I'd still eliminate A if it had "some" rather than "all", for the simple fact that we have no reason to believe that the degree of cooperation in the performance of tasks in naked mole rat colonies differs from the degree of cooperation in task performance in eusocial insect societies. Whether that's one task, some tasks, or all tasks. In other words, I'm hyper focused on what the question was asking, so A (as well as the other wrong answers) is an easy elimination.
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Until recently, scientists did not know of a close vertebrate analogue 27 Oct 2022, 09:43
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For Q1, can you please help me understand how to eliminate option D. I marked D, eliminated C because comparison with eusocial insect societies is just one part. Para 2 and 4 compares it with other vertebrates.


For Q5, to understand why option D is incorrect. As per passage, "(except the wild dog, Lycaon pictus) are dominated by a pair of breeders rather than by a single breeding female." so in Lycaon pictus, it is dominated by single breeding female i.e it is not a cooperative act between pair of breeders and hence D. I eliminated E becasue it could be interpreted as, "not dominated by single pair of dogs" = dominated by multiple pair of dogs but we want single breeding female in the answer choice


For Q7, summary of the passage is
First paragraph ends with the assertion that such a vertebrate society may exist among underground colonies of the naked mole rat.

The rest of the passage explores the similarities/differences in the behavior exhibited by other such vertebrate societies and naked moles:

i) Para-2: Similarity is that naked mole rat colony, like other vertebrate, is ruled by its queen, or reproducing female.
ii) Para-3: Similarities/differences in "cast system" between Eusocial insect societies and naked mole rats.
iii) Para-4: Similarities/differences in "Cooperative breeding" between Eusocial insect societies and naked mole rats

and basis this if we see the larger purpose of the para it is to provide evidence that led to the conclusion mentioned in the first para and hence option D. Can you please correct me
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Until recently, scientists did not know of a close vertebrate analogue 28 Oct 2022, 19:18
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For Q1, can you please help me understand how to eliminate option D. I marked D, eliminated C because comparison with eusocial insect societies is just one part. Para 2 and 4 compares it with other vertebrates.
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Choice D is about "mating habits".

Mating habits are not the main theme of the passage (which is about how naked mole rat societies are organized around a queen, a system more commonly associated with certain insects).

In fact, choice D is far worse still—because most naked mole rats don't even mate at all! Reproduction (and thus mating), as the third paragraph tells us, is "limited to the queen and a few males". The vast majority of naked mole rats—all but one of the females (!), and all the males except the lucky few mentioned here—don't have any "mating habits", because they don't mate.
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Until recently, scientists did not know of a close vertebrate analogue 28 Oct 2022, 19:24
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For Q5, to understand why option D is incorrect. As per passage, "(except the wild dog, Lycaon pictus) are dominated by a pair of breeders rather than by a single breeding female." so in Lycaon pictus, it is dominated by single breeding female i.e it is not a cooperative act between pair of breeders and hence D. I eliminated E becasue it could be interpreted as, "not dominated by single pair of dogs" = dominated by multiple pair of dogs but we want single breeding female in the answer choice
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The passage says...
most cooperatively breeding vertebrates (except the wild dog, Lycaon pictus)...

This part is enough to tell us that the wild dog IS a "cooperatively breeding vertebrate". In any statement that says "[Most] X's, except Y", it's implied that Y is one of the X's.

Similarly,
Most democracies, with Singapore as a notable exception, have specifications for democratic elections written into their constitution or another founding document. —> This statement implies that Singapore is a democracy (but that it doesn't have the specs for its elections written into any of its founding documents).


The answer is E because most of the species mentioned here ARE dominated by a pair of breeders—but the wild dog is the EXCEPTION.
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Until recently, scientists did not know of a close vertebrate analogue 28 Oct 2022, 19:56
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For Q7, summary of the passage is
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Question #7 is only about the third paragraph, so there's no sense in going through the entire paragraph and summarizing every paragraph. You can just jump to the third one—especially because you'll certainly have quite a bit of familiarity with the passage as a whole by this point, having already solved six questions before this one.

Quote:
ii) Para-3: Similarities/differences in "cast system" between Eusocial insect societies and naked mole rats.
Show more

Paragraph 3 is not "similarities and differences"—it's just differences.

Eusocial insect societies have rigid caste systems, each insect's role being defined by its behavior, body shape, and physiology —> NONE of these things is true for the mole rats.
• They don't have a rigid caste system, since the animals can perform certain tasks for a certain period of time and then graduate to other tasks.
• None of these three factors is listed as a determinant of mole rats' role. (Mole rats' roles are determined instead by "reproductive status, body size, and perhaps age".


The passage as a whole is basically an extended analogy between naked mole rats and eusocial insects. So, what's the purpose of a paragraph that points out all the differences?
Those are the aspects of the analogy that DON'T really work. So, overall, this paragraph serves to limit the force of the overall analogy.

"Qualify" as used here means "limit" or "specify more narrowly", so C is the right answer.
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Until recently, scientists did not know of a close vertebrate analogue 06 Nov 2022, 11:15
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Dear GMATNinja
6. According to the passage, naked mole rat colonies may differ from all other known vertebrate groups in which of the following ways?

(A) Naked mole rats exhibit an extreme form of altruism.

(B) Naked mole rats are cooperative breeders.

(C) Among naked mole rats, many males are permitted to breed with a single dominant female.

(D) Among naked mole rats, different tasks are performed at different times in an individual's life.

(E) Among naked mole rats, fighting results in the selection of a breeding female.

In question 6, Can you shed light why choice D & E are wrong?
Question #6 asks how naked mole rats (NMR) differ from "all other known vertebrate groups." So, we are looking for something about naked mole rats that is completely unique to NMRs when compared to all other known vertebrate species.

Let's look first at (D):
Quote:
(D) Among naked mole rats, different tasks are performed at different times in an individual's life.
In the third paragraph, the author states that "in naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status... body size, and perhaps age." He/she then goes on to explain that the size of a particular NMR is a better indicator of what tasks it will complete than is its age -- the NMR's growth rate influences the time they stay in a given task, "regardless of age."

So, at best the information in (D) is only partially true for NMR's. As stated above, we also need proof that NMRs are the only known vertebrates that exhibit the behavior in question. There is simply no evidence in the passage that this is the case for (D). In the last paragraph, we learn that "the division of labor within social groups is less pronounced among other vertebrates than among naked mole rats," but the author doesn't elaborate on how other vertebrates divide their labor. They could split up tasks based on age, in which case (D) would not be unique to NMRs. For this reason, (D) is out.

Now take a look at (E):
Quote:
(E) Among naked mole rats, fighting results in the selection of a breeding female.

Again, we need to prove that this is a unique attribute of NMRs among all known vertebrate groups.

In the last paragraph, the author states that "most cooperatively breeding vertebrates (except the wild dog, Lycaon pictus) are dominated by a pair of breeders rather than by a single breeding female." These cooperatively breeding species must somehow choose which female gets to breed. The passage doesn't tell us how this decision is made, so we cannot be sure that they do not fight to determine which female becomes the breeder. In addition, we have no idea what is going on with the Lycaon pictus -- maybe they fight to choose a single breeding female, or maybe they do not. Because we do not have this information, we cannot say that NMR's differ from all other vertebrate groups in this way. (E) is out.

Compare this to (A):
Quote:
(A) Naked mole rats exhibit an extreme form of altruism.
The evidence for this answer choice is found in the first paragraph: "Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees... However, such a vertebrate society may exist among underground colonies of the highly social rodent Heterocephalus glaber, the naked mole rat."

Here, we learn that scientists did not know of any vertebrates showing an "extreme form of altruism" until they studied NMRs. From this, we can conclude that NMRs are the only known vertebrate group to exhibit this behavior. (A) is the correct answer.

I hope that helps!
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Hi GMATNinja,
Please clarify.
I have a doubt in Choice A. It's asking how Naked Mole Rats differ from other vertebrates. Now as per this line: "Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees... , NMR are similar to Eusocial insects in that they both exhibit extreme form of altruism.So how do they differ?? Please tell me where am I going wrong?

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Niwedita B
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Until recently, scientists did not know of a close vertebrate analogue 05 Dec 2022, 21:31
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Question 6


Bniwedita

Hi GMATNinja,
Please clarify.
I have a doubt in Choice A. It's asking how Naked Mole Rats differ from other vertebrates. Now as per this line: "Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees... , NMR are similar to Eusocial insects in that they both exhibit extreme form of altruism.So how do they differ?? Please tell me where am I going wrong?

Regards,
Niwedita B
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We're interested in how naked mole rat colonies differ from "all other known vertebrate groups."

Let's start by considering a part of the first sentence:

Quote:
Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees..."
Show more
This tells us that insects perform extreme altruism. Until recently, however, there was no known "vertebrate analogue." In other words, until recently, scientists didn't know of a vertebrate that performed "extreme altruism." The passage then tells us that naked mole rats are vertebrates that may perform "extreme altruism."

Let's now consider answer choice (A):

Quote:
6. According to the passage, naked mole rat colonies may differ from all other known vertebrate groups in which of the following ways?

(A) Naked mole rats exhibit an extreme form of altruism.
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As you point out, naked mole rats "are similar to Eusocial insects in that they both exhibit extreme form of altruism." How does this relate to (A)?

Well, based on the passage, we know that insects are NOT vertebrates, and that some of them show extreme altruism. But until recently, there were no known vertebrates that showed extreme altruism. So, since naked mole rats perform extreme altruism, this makes them different than all other known vertebrate groups.

Put another way: before naked mole rats were studied, no vertebrates were known to perform extreme altruism. But now, we know that naked mole rats, who are vertebrates, perform extreme altruism. The fact that insects (who are NOT vertebrates) perform extreme altruism isn't directly relevant.

For all of those reasons, (A) is correct.

I hope that helps!
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Until recently, scientists did not know of a close vertebrate analogue 15 Dec 2022, 20:19
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srishti201996
9 minutes!
one incorrect!

Can someone help please?

question no 6!
Why is the choice C in Q6 wrong?

Cooperative breeding has evolved many times in vertebrates, but unlike naked mole rats, most cooperatively breeding vertebrates (except the wild dog, Lycaon pictus) are dominated by a pair of breeders rather than by a single breeding female.
In naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status (reproduction being limited to the queen and a few males

Doesn't the sentence mentioned above reflect the fact stated in option C?
(C) Among naked mole rats, many males are permitted to breed with a single dominant female.
Quote:
6. According to the passage, naked mole rat colonies may differ from all other known vertebrate groups in which of the following ways?

(A) Naked mole rats exhibit an extreme form of altruism.

(B) Naked mole rats are cooperative breeders.

(C) Among naked mole rats, many males are permitted to breed with a single dominant female.

(D) Among naked mole rats, different tasks are performed at different times in an individual's life.

(E) Among naked mole rats, fighting results in the selection of a breeding female.
The answer lies in the 2nd BF portion: "reproduction being limited to the queen and a few males."

Among naked mole rats, only a few males (not many) breed with a single dominant female. Thus, (C) does not accurately describe the naked mole rats.

Furthermore, we are told that "most (not all)cooperatively breeding vertebrates are dominated by a pair of breeders rather than by a single breeding female. This suggests that some other cooperatively breeding vertebrates have a single breeding female. Thus, this feature would NOT be unique to naked mole rats.

(C) can be eliminated.

I hope that helps!
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But, if we look at the first line of the paragraph, it says that - "Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees"
It means that the extreme form of altruism is already observed in other insects such as ants & bees.
Q6 asks - how naked mole rats differ from other vertebrates.
So definitely, we can't say that they(naked mole rats) are the only ones to exhibit extreme altruism because scientists were looking for species that exhibit extreme altruism which they have already observed in ants & bees.

Please help.
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Until recently, scientists did not know of a close vertebrate analogue 20 Dec 2022, 14:41
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GMATNinja
srishti201996
9 minutes!
one incorrect!

Can someone help please?

question no 6!
Why is the choice C in Q6 wrong?

Cooperative breeding has evolved many times in vertebrates, but unlike naked mole rats, most cooperatively breeding vertebrates (except the wild dog, Lycaon pictus) are dominated by a pair of breeders rather than by a single breeding female.
In naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status (reproduction being limited to the queen and a few males

Doesn't the sentence mentioned above reflect the fact stated in option C?
(C) Among naked mole rats, many males are permitted to breed with a single dominant female.
Quote:
6. According to the passage, naked mole rat colonies may differ from all other known vertebrate groups in which of the following ways?

(A) Naked mole rats exhibit an extreme form of altruism.

(B) Naked mole rats are cooperative breeders.

(C) Among naked mole rats, many males are permitted to breed with a single dominant female.

(D) Among naked mole rats, different tasks are performed at different times in an individual's life.

(E) Among naked mole rats, fighting results in the selection of a breeding female.
The answer lies in the 2nd BF portion: "reproduction being limited to the queen and a few males."

Among naked mole rats, only a few males (not many) breed with a single dominant female. Thus, (C) does not accurately describe the naked mole rats.

Furthermore, we are told that "most (not all)cooperatively breeding vertebrates are dominated by a pair of breeders rather than by a single breeding female. This suggests that some other cooperatively breeding vertebrates have a single breeding female. Thus, this feature would NOT be unique to naked mole rats.

(C) can be eliminated.

I hope that helps!

But, if we look at the first line of the paragraph, it says that - "Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees"
It means that the extreme form of altruism is already observed in other insects such as ants & bees.
Q6 asks - how naked mole rats differ from other vertebrates.
So definitely, we can't say that they(naked mole rats) are the only ones to exhibit extreme altruism because scientists were looking for species that exhibit extreme altruism which they have already observed in ants & bees.

Please help.
GMATNinja
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"Vertebrates" are animals with backbones. The insects mentioned in the first sentence don't have backbones, so they are not vertebrates. So, while these invertebrates show extreme altruism, the naked mole rat is the only known vertebrate species to exhibit an extreme form of altruism.

That's why (A) is correct for question 6.

I hope that helps!
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Until recently, scientists did not know of a close vertebrate analogue 07 Jun 2023, 05:09
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1. The correct answer is (C) "Behavior in naked mole rat colonies may well be a close vertebrate analogue to behavior in eusocial insect societies." This is supported by the passage's description of the similarities between the extreme altruism observed in eusocial insects and the behavior of naked mole rat colonies.

2. The correct answer is (B) "Age." The passage mentions that Jarvis' work suggests that differences in growth rates may influence the length of time an individual performs a task, regardless of its age. This challenges the assumption that age alone is the determining factor for task performance.

3. The correct answer is (B) "In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape." The passage states that differences in behavior among naked mole rat colonies are primarily related to reproductive status, body size, and possibly age, rather than body shape. This indicates that task performance is less rigidly tied to body shape in naked mole rat colonies compared to eusocial insect societies.

4. The correct answer is (B) "She exerts chemical control over the colony." The passage mentions that the queen maintains her breeding status through a mixture of behavioral and presumed chemical control. While the passage does not explicitly state that she exerts chemical control, it implies that chemical control is a likely mechanism for maintaining her reproductive dominance.

5. The correct answer is (E) "Breeding is not dominated by a single pair of dogs." The passage mentions that Lycaon pictus, the wild dog, is an exception among cooperatively breeding vertebrates, as breeding is dominated by a pair of breeders rather than a single female. This suggests that breeding in the social group is not dominated by a single pair of dogs.

6. The correct answer is (A) "Naked mole rats exhibit an extreme form of altruism." The passage describes the extreme form of altruism observed in naked mole rat colonies, where individuals cooperate and sometimes sacrifice their own opportunities for the good of others. This distinguishes naked mole rats from other known vertebrate groups.

7. The correct answer is (C) "Qualify the extent to which two previously mentioned groups might be similar." The third paragraph of the passage contrasts the rigid caste systems in eusocial insect societies with the differences in behavior related primarily to reproductive status, body size, and possibly age in naked mole rat colonies. This qualifies the extent to which the two groups might be similar in terms of their social organization and division of labor.
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Until recently, scientists did not know of a close vertebrate analogue 13 Jun 2025, 08:04
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