Harvester-ant colonies live for fifteen to twenty years though indivi

Question

Harvester-ant colonies live for fifteen to twenty years, though individual worker ants live only a year. The way a colony behaves changes steadily in a predictable pattern as the colony grows older and larger. For the first few years, the foragers behave quite aggressively, searching out and vigorously defending new food sources, but once a colony has reached a certain size, its foragers become considerably less aggressive.

If the statements above are true, which of the following can most properly be concluded on the basis of them?

A) As a result of pressure from neighbors, some colonies do not grow larger as they become older.

B) Unpredictable changes in a colony's environment can cause changes in the tasks that the colony must perform if it is to continue to survive.

C) The reason a mature colony goes out of existence is that younger, more aggressive colonies successfully outcompete it for food.

D) The pattern of changing behavior that a colony displays does not arise from a change in the behavior of any individual worker ant or group of worker ants.

E) A new colony comes into existence when a group of young, aggressive workers leaves a mature colony and sets up on its own.

ID: 500275
CR09740.02

Beylo · Accepted Answer

Nice question!

Objective: What can i conclude?
Evidence. Colonies live 10-20years, individual ants 1year... Early years ++ Aggressive , later year -- Aggressive

A) As a result of pressure from neighbors, some colonies do not grow larger as they become older.

We don't know this. Maybe its true but we have no evidence!

B) Unpredictable changes in a colony's environment can cause changes in the tasks that the colony must perform if it is to continue to survive.

Maybe! But we don't know this with the evidence!

C) The reason a mature colony goes out of existence is that younger, more aggressive colonies successfully outcompete it for food.

Such a tricky answer! Yes, it can be true! But we are making an assumption of the older colonies behavior. Do they need to forage for food? Maybe they have a self-sustainig colony. Or maybe de do die! We don't know

D) The pattern of changing behavior that a colony displays does not arise from a change in the behavior of any individual worker ant or group of worker ants.

So easy to eliminate! But the only answer we know is true! Because ants live only 1 year.... no one ant or group of them will influence the behavior of the colony as it ages. Every year new ants are inferred to be born. Correct answer!

E) A new colony comes into existence when a group of young, aggressive workers leaves a mature colony and sets up on its own.

Maybe! But we don't know with the evidence. Chuck the answer move on with your life.

Select D and move forward!

C
D
E

C D E

itspC · Answer

OFFICIAL SOLUTION(OG^c Version):

Argument Construction Situation

The given information contrasts the lifespan of harvester-ant colonies (twenty years) with that of individual forager in the colonies (one year). When the colony is young and relatively small, its foragers aggressively seek and defend food resources. But when the colony grows older and reaches a certain size, its foragers become less aggressive

Reasoning

Which choice is so strongly supported by the given information Obviously, the survival of a colony can be jeopardized by encountering unusual environmental challenges. But the given information suggests that provided no unusual threats to the colony's survival are encountered, a colony's life cycle is biologically determined by constraints of colony size and age. The behavior of the individual forgers is correlated with the age and size of the colony, how a forager behaves in a colony near its maximum limits of the site, and age is quite different from an individual forager's behavior in the colonies early years.
 The behaviors of individual foragers are highly coordinated: the patterns of behavior of the colony are not caused by individual behaviors of the worker 
 ants

A)Although this might be true, the given information suggests that the limits on colony size do not depend on competition from neighbors but are, rather, general constraints that are based in harvester-ant biology

B)Although this is likely true, the given information does not address the issue of how colony dynamics might be affected by drastic and unusual environmental changes.

C)Obviously, the survival of a colony that fails over a period to secure the food resources it needs would be threatened. But the given information not state or imply that such failures are generally due to more aggressive competition by ants in another colony. It suggests that, in general, a colony's demise is primarily dictated by the biological constraints on colony size and age.

D)Correct. As explained, the given information suggests that provided no unusual threats to a colony's survival are encountered, its life cycle is biologically determined by constraints of colony size and age, not by the behavior of individual forager ants or groups of such ants. The given information suggests that the biological constraints on a colony's size and longevity also determine the behavior of individual worker ants, who live about one year

E)Nothing in the given information suggests that worker ants are the founders of a harvester-ant colony.

The correct answer is D.

Pro Tip:(Not to fall for a trap): Conclusion questions are inference questions, but the inference should never be out of passage info and never slip out from Gist of passage. Don't get your general knowledge and intuition(out of passage) into such info questions

SR71Blackbird · Answer

Simple question if you think minimal and nothing more. Ant colony can live upto a decade but ants can only live upto an year. At the start, ants are fierce but as the colony grows they calm down gradually. Now, we have to conclude what does this info can come to. A) We don't know. It could be neighbors, it could be animals or even evnironment. Cannot conclude. B) We don't know. No where it is mentioned regarding role changing depending on environemental factors. Cannot Conclude. C) We don't know. What if the colony goes out of existence because the food sources have depleted, or the conditions are no more suitable to grow anymore or maybe an infection outbreak has occurred. Younger colonies is one of the reasons but cannot be the only reason. D) Correct. Since ants live only for a year, their behavior has no influence on the colony behavior after, lets say, 3 years or even after 5 years. The changing behavior occurs with each subsequent formation of a new younger generation and the behavior is not carried on from one generation to another because it's a gradual change in behavior taking many years. E) We don't know. No info on it. ( Plus ants are very loyal, young ants just cannot rebel

)

yatindra20 · Answer

VeritasPrepHailey  Could you please help in this question.

IMO this is and inference question.

I would love to understand how you tackle or what is your strategy to deal with inference questions.

CrackverbalGMAT · Answer

Hi Yatindra

Let me try and provide some inputs on this front.

The key to identifying the answer in an inference based question (as you have correctly identified this to be) is that every single part of the correct answer must be  100% supported  by information given in the passage / stimulus. It is not sufficient if the option  may be true  - the option  must be undeniably true  based on the information given for it to be a valid inference.

For eg; consider the sentence: The instructor walked into the class with his hair wet.

We cannot infer any of the following from the above statement:

a) It is raining outside.
b) Someone played a prank on the instructor.
c) The instructor came running so the hair is wet with sweat.

Each of the above only may be true - it is also possible that they are not true (for eg; since each of the above provides an alternate explanation for the hair being wet than the other two).

Considering this, let us analyse the answer options given:

A) As a result of pressure from neighbors, some colonies do not grow larger as they become older.  There is nothing in the stimulus about pressure from neighbours or the size of older colonies. Eliminate.

B) Unpredictable changes in a colony's environment can cause changes in the tasks that the colony must perform if it is to continue to survive.  There is nothing in the stimulus about any changes to the environment or its impact. Eliminate.

C) The reason a mature colony goes out of existence is that younger, more aggressive colonies successfully outcompete it for food.  While it is true that older colonies become less aggressive, the stimulus does not say anything about whether this is the reason for them going out of existence. Eliminate.

D) The pattern of changing behavior that a colony displays does not arise from a change in the behavior of any individual worker ant or group of worker ants.  This is the correct answer. If you notice, every single part of the answer option is supported by the stimulus. There is "a pattern of changing behaviour" of colonies. The passage states "its foragers become considerably less aggressive" implying this to be true of most or all foragers (ie; worker ants). Hence this change in behaviour is not due to "change in the behavior of any individual worker ant or group of worker ants".

E) A new colony comes into existence when a group of young, aggressive workers leaves a mature colony and sets up on its own.  There is nothing in the stimulus about how a new colony is formed. Eliminate.

Hope this helps.

mSKR · Answer

Can some one clarify that :
I. harvester-ant colonies comprises of : worker ants + foragers + harvester ants? 
II. or harvester-ant colonies = group of worker ants. Worker ants are foragers and are harvester ants.

If II. then as per D option , with time new worker ants would have change in their behavior as compared to dead worker ants ( less aggressive). It means group of grand= ant babies bring a change in their patters.
Or D means : bring a change in present time of their life time.

B) Unpredictable changes in a colony's environment can cause changes in the tasks that the colony must perform if it is to continue to survive.

B says if ants need to survive then ants should be ready for any changes. In 15-20 years, they could not cope with changes as they become less aggressive and when they need to have more aggression but could not aggressive then these colonies wipe out.

I am kind of lost in B and D. Maybe I need a small break from this question and come back again later again.

Please suggest  VeritasKarishma   AndrewN  sir. 
Please also suggest how to avoid overthinking in such questions and how can I reach to correct in this particular question in quickest time.

thanks!

AndrewN · Answer

Hello,  imSKR . In the passage, we are meant to conflate  harvester ant ,  worker ant , and  forager ant . How do we know? We can deduce that  individual worker ants  comprise the  harvester-ant colonies  that are mentioned just before in the opening line. Meanwhile,  its foragers  in the final line clearly points back to  a colony , and since the only type of colony that has been mentioned is one made of harvester ants, we can put all the pieces together. You could argue that foragers might represent a specific subcategory of worker ant, but that is beside the point: to forage is to perform some sort of work. With that behind us, how about we consider choices (B) and (D)?

The problem I have with choice (B) starts at the first two words,  unpredictable changes . On what basis are we qualified to say anything about how the colony reacts to such changes? In fact, the passage only offers that  the way a colony behaves changes steadily in a predictable pattern . I did not take my analysis any further with this one.

Choice (D) is supportable from the information given in the first line of the passage. If  individual worker ants live only a year , but their colonies  live for fifteen to twenty years , then it is safe to say that any individual ant will not fall out of line with where the colony is within its predictable pattern of steady change. Neither can any group of such ants do anything radical that would disturb the predictable correlation between the age and size of a colony (or else the predictability would be ruined). This is the hardest answer to argue against, so it is the winner of the bunch.

In order to avoid overthinking, seek simple one-to-one relationships between the passage and the keywords of the answer choices. You get into trouble when you start interpreting the language of the passage or delving into associative thinking. Just stick to the surface of what the passage says, get rid of any answer that clearly falls out of bounds, and if you arrive at a 50/50 proposition, ask yourself which answer is harder to argue against. Look at the passage and compare one, two, even three times, if necessary. Do not get behind an answer simply because you like one part of it better than another, safer bet, when considered as a whole. An answer that is even 90 percent correct is still 100 percent wrong.

Thank you for thinking to ask me about this one. I hope that helps.

- Andrew

KarishmaB · Answer

Video solution to this question: https://youtu.be/g_A0LGiDmnk Harvester-ant colonies live for 15-20 yrs Individual worker ants live only a year. The way a colony behaves changes steadily in a predictable pattern as the colony grows older and larger. For the first few years, the foragers behave quite aggressively, searching out and vigorously defending new food sources. Once a colony has reached a certain size, its foragers become considerably less aggressive. The colony's age and size determine how the foragers behave. They live for only 1 year so every year, there is a new work force. Their behaviour is dictated by the colony age and size. If the colony is new and small, they are aggressive. If the colony is old and big, they are passive. The point being made here is clearly that the workers' behaviour does not dictate their actions (whether they are passive or active). It is the colony size that does. What can we conclude? A) As a result of pressure from neighbors, some colonies do not grow larger as they become older. The argument does not talk about pressure from neighbours. B) Unpredictable changes in a colony's environment can cause changes in the tasks that the colony must perform if it is to continue to survive. No support in the argument. C) The reason a mature colony goes out of existence is that younger, more aggressive colonies successfully outcompete it for food. This is sound reason and seems to make sense as per the argument but the argument does not mention why a mature colony goes out of existence. It just says that in a mature colony, the foragers are not aggressive. But they may still be providing enough. The argument doesn't tell us why a colony has a life of 15-20 yrs. Perhaps it has something to do with lifecycle of an ant - whatever. D) The pattern of changing behavior that a colony displays does not arise from a change in the behavior of any individual worker ant or group of worker ants. Correct. The pattern of changing behaviour of a colony is a function of its own size and age, not of the behaviour of any one or group of ants. Ants behave as per the size and age of the colony. Their behaviour does not change. Ants change (new ones come every year). E) A new colony comes into existence when a group of young, aggressive workers leaves a mature colony and sets up on its own. We don't know how and when a new colony comes into existence. Nothing mentioned about ants leaving a colony. Answer (D)

jabhatta2 · Answer

Hi  avigutman  - while I agree A/B/C and E are wrong, I thought D had a flaw - The answer should be 100 % inferable.

The phrase in D  Does not arise  is too strong imo
 
I read that  change of behaviour  occurs as the  colony ages / colony grows .

Per my understanding, the author is talking about a correlation in the bold above - 
- Two actions (action in purple above / action in red above) are seen happening concurrently.

The author  does not claim  the action in  red  is causing the  purple

Thus, we actually DON’T KNOW 
- What are logical causes for why these two actions (action in purple / action in red) are seen concurrently

Also, we don’t know who first initiates this change 
- Perhaps, the queen of colony instructs the worker ants. 
- Perhaps, all the ants (who only live for 1 year) do so on their own 
- Perhaps some worker ants (who only live for 1 year) initiate and the other worker ants just follow 
- Who knos....

Thus when I read D – I thought we cannot definitively say that the ants DO NOT CAUSE this change for 2 reasons

- We actually don’t know who or what initiates the action in purple 
- Maybe 1 year is enough to bring about a change (the passage doesnt say anything about how long anything takes...)

Thus I did have this reservation on D, we just dont know

Thoughts

avigutman · Answer

It’s true we don’t know who or what initiates the action in purple. Nevertheless, we can rule out the individual ants (we know they live ONLY one year) thanks to this:

“For the first few years, the foragers behave quite aggressively, searching out and vigorously defending new food sources, but once a colony has reached a certain size…”

As you can see in the quoted text, we actually do know how long the change takes.

Posted from my mobile device

jabhatta2 · Answer

Thank you  avigutman  - having read the quote, could you please let me how you interpret the first 9 words in option D

Assuming there are 3 time periods,

Time period 1) foragers are quite aggressive
Time period 2) behavior starts changing 
Time period 3) foragers are less aggressive

Do the words in red above refers to time periods OVER the entire lifecycle of the colony (i.e. over 20 years) OR just the first two time periods (time period 1 + time period 2) ?

I think its time period 1 + time period 2 only (not all 3 time period)

Thus no one ant CAN live OVER 2 time periods

avigutman · Answer

jabhatta2  there's only one way to interpret those 9 words. Note the article "the" at the start. This implies that whatever this pattern is, it's something specific that we should already know about. Looking back at the passage, there's only one pattern mentioned, so it must be that one:

The way a colony behaves changes steadily in a predictable  pattern  as the colony grows older and larger.

Based on that, my interpretation is that we're talking about the entire 15-20 years.

Namangupta1997 · Answer

avigutman  
The passage says that the colony has a life of 15-20 years. Suppose a colony is about to end and is in the 14th year ( assuming a life span of 15 years). Now if new worker ants are born in the mid of 14th year, they will spend half of their lives (6 months) in the existing colony. Now they still have another 6 months to live. This group of worker ants now, who have 6 more months to live, can potentially start a new colony. Wouldn't that make option D incorrect ?

avigutman · Answer

Why would this scenario go against answer choice (D),  Namangupta1997 ? 
Answer choice (D) is talking about the changing behavior of an existing colony, not about a new colony.

Bunuel · Answer

Yes, it is. You can check question category in the tags just above the first post:

Gemmie · Answer

The passage highlights a fascinating phenomenon - harvester ant colonies display a predictable shift in foraging behavior as they age. Young colonies have aggressive foragers, while older, larger colonies have less aggressive ones.

D is the Best Conclusion:

==> Individual Lifespan vs. Colony Behavior Change:  The passage tells us individual worker ants only live a year, while the colony lasts 15-20 years. This implies the colony behavior change isn't due to individual ants "aging" and becoming less aggressive. New, young ants are constantly born, so the individual ants themselves shouldn't explain the colony-wide shift.

Ruling Out Other Options:

A) Neighbor Pressure:  The passage doesn't mention competition with neighbors affecting colony growth.

B) Environmental Changes:  While true, the passage focuses on age-related behavior changes, not external factors.

C) Colony Competition:  We only know the behavior changes, not aggressive competition causing extinction of older colonies.

E) Colony Formation:  The passage doesn't directly explain how new colonies form, just the behavior shift within existing ones.

Dbrunik · Answer

This is a high quality question and i agree with the solution.

i initially got this question wrong, and narrowed it down to B and D. my logic was that B made sense because "unpredictable changes" would warrant the aggression as discussed in the passage. Of course, this answer, might be true, but it doesnt actually mention what those unpredictable changes are. This answer choice simply "sounds good" but does not tie back to the prompt.

I am not quite sure why i ruled out B, i suppose that when reading "The pattern of changing behavior that a colony displays does not arise from a change in the behavior of any individual worker ant or group of worker ants." i thought that the pattern of behavior going from aggressive to not, was dictated by that group of forager ants.

official solution to D:. Correct. As explained, the given information suggests that, provided no unusual threats to a colony’s survival are encountered, its life cycle is biologically determined by constraints of colony size and age, not by the behavior of individual forager ants or groups of such ants. The given information suggests that the biological constraints on a colony’s size and longevity also determine behaviors of individual worker ants, who live about one year.

DrMock · Answer

Couldn't it be the case that every batch of forager/worker ants influenced the next batch and that it cascaded accordingly? Similarly, simply because they died doesn't mean they haven't influenced future generations.

WhitEngagePrep · Answer

I'm actually going to disagree quite strongly with some of the folks above and say that I think this "correct" answer is terribly worded and wouldn't pass a gmat-writer's test. The fact is that c hoice (D) overreaches (in ways that the actual test never would). The stimulus warrants saying that the same individual ants cannot be responsible for the behavioral shift (they die within a year), but it does not justify the blanket claim that the change “does not arise from a change in the behavior of any ... group of worker ants.” In fact, the forager caste itself is a group whose collective behavior plainly changes from aggressive to less aggressive. Thus (D) is technically contradicted by the very facts given, yet the other four options introduce completely new speculations; we are forced to select (D) only because it is the least unsupported , not because it is fully correct.

Whit

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