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

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 )

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.

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.

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!

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

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)

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 [Please correct me if i am wrong on this point]

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

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

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

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.

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 ?

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.

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

­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.­

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.