Until recently, scientists did not know of a close vertebrate analogue

Hi Vishal, 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.

Hence, throughout the passage, the author is trying to make a point that behavior in naked mole rat colonies may well be a "close vertebrate analogue" (not "same" but "close") to behavior in eusocial insect societies.

The evidence for (A) is much more plainly stated in the first paragraph: scientists didn't know about any vertebrate species that were as altruistic as ants/bees, but then they found that this altruism may exist in NMR society. The next paragraphs confirm that NMR's are altruistic by providing specific examples (the colony is ruled by a queen, none of the other females reproduce, tasks are split up among colony members, etc).

The sentence that you've quoted is yet another example of how altruistic NMR's are -- whereas other species allow some non-queen females to reproduce, the NMR society the non-queen females don't reproduce at all, and instead serve the needs of the colony.

So yes, that sentence provides evidence to support (A) for question 6. However, if you understand the overall structure of the passage then you don't need to leap from that evidence to the inference that "naked mole rats exhibit an extreme form of altruism" -- the author already states this at the beginning of the passage, and then spends the rest of the passage backing up this assertion with examples.

I hope that helps!

Dear GMATNinja KarishmaB
I am unable to differentiate between a supposition and a fact here. Does supposition means ASSUMPTION ?
How is the answer B ? The passage gives information that


Could you please explain why the answer is B here ?

We are given:
The queen is the largest member of the colony, and she maintains her breeding status through a mixture of behavioral and, presumably, chemical control.

The use of the word "presumably" tells us that the queen uses chemical control is an assumption (the way it is used in common parlance, not CR), not a known fact. It seems from the available data that she uses chemical control but we can't say for sure.
A supposition is something supposed/assumed. It is not established as a fact.

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."

Can we use our outside knowledge to differentiate between, an insect and a vertebrate?
Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects.

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.)


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).


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):


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):


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.

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."

Does my point above clarify all of that?
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.
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.

Hi avigutman

Thank you for your explanations!!!

You always catch something I never gave a serious thought in the RC passage or CR stimulus--I just lightly thought that "body shape" is equivalent to "body size." Many of my doubts disappeared once I realized that the two terms are not necessarily equivalent: so yes it makes sense to pick the option (B) as rats care about the body size for job distribution instead of the body shape, and yes it makes sense for the author to use the idiom "on the other hand" in the third paragraph, since he or she does talk about different factors for the two societies. Thank you for helping me understand that.


Thank you for sharing this tip! I know that it is important to answer questions as efficiently as possible since the test is timed, and I think following this guidance would help me be more efficient.

Really appreciate your time, explanations and insights.

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

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.

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.

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.


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.

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

This passage proves that you really have to go deep ,and base your understanding on the facts. Q6. is quite difficult and it was really difficult to eliminate option D until I read @gmatninja's explanation. Quite deep.

Question 6

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:

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):

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!

GMATNinja

sir can you explain Q7

Explained here by GMATNinja

https://gmatclub.com/forum/until-recent ... l#p2733442

Best