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

Question

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

(A) Naked mole rat colonies are the only known examples of cooperatively breeding vertebrate societies. 
(B) Naked mole rat colonies exhibit social organization based on a rigid caste system. 
(C) Behavior in naked mole rat colonies may well be a close vertebrate analogue to behavior in eusocial insect societies. 
(D) The mating habits of naked mole rats differ from those of any other vertebrate species. 
(E) The basis for the division of labor among naked mole rats is the same as that among eusocial insects.

2 
2. The passage suggests that Jarvis' work has called into question which of the following explanatory variables for naked mole rat behavior?
 
(A) Size 
(B) Age 
(C) Reproductive status 
(D) Rate of growth 
(E) Previously exhibited behavior

3 
 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.

4 
 4. According to the passage, which of the following is a supposition rather than a fact concerning the queen in a naked mole rat colony?

(A) She is the largest member of the colony. 
(B) She exerts chemical control over the colony. 
(C) She mates with more than one male. 
(D) She attains her status through aggression. 
(E) She is the only breeding female.

5 
 5. The passage supports which of the following inferences about breeding among Lycaon pictus?

(A) The largest female in the social group does not maintain reproductive status by means of behavioral control. 
(B) An individual's ability to breed is related primarily to its rate of growth. 
(C) Breeding is the only task performed by the breeding female. 
(D) Breeding in the social group is not cooperative. 
(E) Breeding is not dominated by a single pair of dogs.

6 
 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.

7 
 7. One function of the third paragraph of the passage is to

(A) state a conclusion about facts presented in an earlier paragraph 
(B) introduce information that is contradicted by information in the fourth paragraph 
(C) qualify the extent to which two previously mentioned groups might be similar 
(D) show the chain of reasoning that led to the conclusions of a specific study 
(E) demonstrate that of three explanatory factors offered, two may be of equal significance

Poorvasha · Accepted Answer

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

(A) Naked mole rat colonies are the only known examples of cooperatively breeding vertebrate societies.

(B) Naked mole rat colonies exhibit social organization based on a rigid caste system.

(C) Behavior in naked mole rat colonies may well be a close vertebrate analogue to behavior in eusocial insect societies. -  The passage begins by stating 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, 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 ." Then the passage further points out the similarities between the naked mole rat and eusocial insects in the subsequent passages. It points certain differences also but says its behavior still remains closest to a naked mole rat.
 
(D) The mating habits of naked mole rats differ from those of any other vertebrate species.

(E) The basis for the division of labor among naked mole rats is the same as that among eusocial insects.

OA:C

2. The passage suggests that Jarvis' work has called into question which of the following explanatory variables for naked mole rat behavior?

(A) Size

(B) Age -  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 .

(C) Reproductive status

(D) Rate of growth

(E) Previously exhibited behavior

OA:B

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 ate performed cooperatively.

(B) In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape. -  1. Eusocial insect societies have  rigid caste systems , each insect's role being defined by its behavior, body shape, and physiology
2. 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

(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.

OA:B

4. According to the passage, which of the following is a supposition rather than a fact concerning the queen in a naked mole rat colony?

(A) She is the largest member of the colony.

(B) She exerts chemical control over the colony. -  queen is the largest member of the colony, and she maintains her breeding status through a mixture of behavioral and,  presumably , chemical control
 
(C) She mates with more than one male.

(D) She attains her status through aggression.

(E) She is the only breeding female.

OA:B

5. The passage supports which of the following inferences about breeding among Lycaon pictus?

(A) The largest female in the social group does not maintain reproductive status by means of behavioral control.

(B) An individual's ability to breed is related primarily to its rate of growth.

(C) Breeding is the only task performed by the breeding female.

(D) Breeding in the social group is not cooperative.

(E) Breeding is not dominated by a single pair of dogs. -  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
 
 OA:E

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. -  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 .

(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.

OA:A

7. One function of the third paragraph of the passage is to

(A) state a conclusion about facts presented in an earlier paragraph

(B) introduce information that is contradicted by information in the fourth paragraph

(C) qualify the extent to which two previously mentioned groups might be similar -  The two previously mentioned groups are the naked mole rat and the eusocial insects. The third para states to what extent are they similar. It states that: "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."

(D) show the chain of reasoning that led to the conclusions of a specific study

(E) demonstrate that of three explanatory factors offered, two may be of equal significance

OA:C

GMATNinja · Answer

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!

gabesc87 · Answer

Hi,

Not getting why 3 is not D: it's always talking about one queen mainly. I though about B but the passage states that "in naked mole rat colonies, the performance of tasks are determined by reproductive status, body size, and perhaps age" but not body shape.

And in 7, where is the author qualifying?

Poorvasha · Answer

Hi  gabesc87 ,

For Question 3: Option B says "In naked mole rat colonies, the performance of tasks is less rigidly determined by body shape". To evaluate this focus on the below to sentences of the passage.:
1. Eusocial insect societies have rigid caste systems, each insect's role being defined by its behavior, body shape, and physiology
2. 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
 This implies that eusocial insects have more rigid cast systems and their role is defined by 3 factors including body shape. In naked mole rat, on the other hand, differences in behavior is related PRIMARILY to reproductive status. Body size, age etc are secondary. So, since body shape is a rigid and primary factor for eusocial insects and since, it is a secondary factor for naked mole rats, this automatically implies body shape as a factor is less rigid in mole rats. . Hence, B is correct.

(D) In eusocial insect societies, reproduction is limited to a single female. - No where is this stated in the passage.

Question 7: C: "qualify the extent to which two previously mentioned groups might be similar" - The two previously mentioned groups are the naked mole rat and the eusocial insects. The third para states to what extent are they similar. It states that: "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."  Thus, the author is talking about the extent to which these two groups are similar in characteristics. This is what the author is qualifying.

Hope this helps!

srishti201996 · Answer

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.

Mo2men · Answer

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?

GMATNinja · Answer

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):
 
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):
 
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):
 
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!

sunny91 · Answer

Skywalker18 ,
can u kindly explain question no 2- I thought the answer is size.

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.

According to my understanding,Jarvis did not agree that the large size is the reason for large non breeders to work. It's the growth rate that matters.

Skywalker18 · Answer

Hi sunny91,
2. The passage suggests that Jarvis' work has called into question which of the following explanatory variables for naked mole rat behavior?

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. --> age is one of the factors in naked mole rat societies

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 . ---> As per Jarvis, age is not a factor that influences differences in behavior in Naked mole rat societies

himanshurajawat · Answer

In Q6. why is A correct?
The passage states 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... However, such a vertebrate society may exist among underground colonies of the highly social rodent Heterocephalus glaber, the naked mole rat."
If ants and bees already diplay extreme form of altruism, how can naked mole rats be different from them in this respect?

SajjadAhmad   u1983   workout   GMATNinja   GMATNinja Two  Gnpth   Bunuel   VeritasKarishma

KarishmaB · Answer

We need them to be different from all other 'vertebrate' groups.

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...

They knew of insects with extreme form of altruism but not a vertebrate. Then they found naked mole rat.

arya251294 · Answer

GMATNinja  Hi there,

Sorry to bother you, but, I believe in Q6 - 
  
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.

As you said, we have to look for something which talks about the unique characteristic of NMRs why can't option (C) serve to be the right one? As nowhere it is mentioned that apart from NMRs, other vertebrates also had multiple males breeding with single female.

Also for Q7 -

7. One function of the third paragraph of the passage is to

(A) state a conclusion about facts presented in an earlier paragraph

(B) introduce information that is contradicted by information in the fourth paragraph

(C) qualify the extent to which two previously mentioned groups might be similar

(D) show the chain of reasoning that led to the conclusions of a specific study

(E) demonstrate that of three explanatory factors offered, two may be of equal significance
  
IMO the third para shows the difference between the 2 groups and not the similarities. Please help.

GMATNinja · Answer

Question 7 
 
Have you had a chance to look at our  previous post  on (C) for question 6? In that post, we identify a couple reasons to eliminate (C).

Regarding question 7, your understanding of the third paragraph does not seem to be off, but perhaps you didn’t catch exactly what (C) means.

In this context, “to qualify” means “to make (a statement or assertion) less absolute or add reservations to.” So when (C) says that the third paragraph qualifies the extent to which two previously mentioned groups (eurosocial insects and naked mole rats) might be similar, it means that the paragraph adds reservations to the comparison between those two groups.

In other words, (C) suggests that the third paragraph shows how the similarities between naked mole rats and eurosocial insects are limited. Because that is, indeed, the function of the third paragraph, (C) is the best answer choice.

I hope that helps!

Vishalcv · Answer

Hello Sir  EducationAisle

I desperately need some help here, Sir.

Of the 7, I got 1 wrong, and the one I got wrong was probably the easiest of the lot, the first one. The passage states that an analogous vertebrate has been found, in the first paragraph only. However, in the subsequent paragraphs, the points of discussion have been purely about:

1. Reproduction aspects of the naked mole rat.
2. How they are different from other vertebrates.

The answer to the main point of the passage must point to the entire passage. However, here, that is not the case. How can the answer be C when only the first paragraph discusses the similarity. Due to obvious reasons, I chose D. I am starting to wonder if I should change the way I approach 'easy' questions with my GMAT 3 days away. Also, do main point or primary purpose questions always point to what the entire paragraph discusses.

Thanks a ton in advance

JatinAgharaGmat · Answer

GMATNinja

I am bit confused here. I choose A but my reasoning was:

'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.'

this is mentioned in last sentence of last paragraph so I thought it shows that Naked mole rats exhibit an extreme form of altruism. was my inference reasonable here?

EducationAisle · Answer

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.

GMATNinja · Answer

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!

lostminer · Answer

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 ?

KarishmaB · Answer

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

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

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