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# In order to withstand tidal currents, juvenile horseshoe

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Re: In order to withstand tidal currents, juvenile horseshoe [#permalink]

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27 Aug 2012, 12:53
noboru wrote:
In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles from clinging to their shells. When fully grown, however, the crabs can readily withstand tidal currents without burrowing, and thus they acquire substantial populations of barnacles. Surprisingly, in areas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow.

Which of the following, if true, most helps to explain the surprising finding?

(A) Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs.
(B) Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.
(C) The strength of the tidal currents in a given location varies widely over the course of a day.
(D) A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.
(E) Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.

I had a really hard time understanding Choice A. I'm wondering if my thought process is correct in disqualifying A now.

Here's how I understand the argument:
- high tidal waves --> more burrowing for juvenile horseshoe crabs --> decreased barnacles
BUT ALSO
- low tidal waves --> less burrowing for juvenile horseshoe crabs --> decreased barnacles
how can this be?

A. Tells us that the water tides don't matter. So the less or more barnacle populations have to do with burrowing then (given the premises). So we are left with the situation where:
- more burrowing --> less barnacle population
- less burrowing --> less barnacle population

Is this accurate?
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Re: In order to withstand tidal currents, juvenile horseshoe [#permalink]

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30 Aug 2012, 00:57
A really good question. Going through the above posts I understand that this one is from OG12. Took me a really long time at close to 3 mins to reach E. I had to re-read the question stem to resolve this one.

The key to this question is spotting the word "Juvenile". The last statement is about the "juvenile" crabs and not the full grown ones. This makes the statement about full-grown crabs not having to burrow irrelevant in the given argument.

E correctly gives us a reason as to why not a large population of barnacles was not found i.e. since the juvenile crabs shed their shells regularly till full grown.
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Re: In order to withstand tidal currents, juvenile horseshoe [#permalink]

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30 Aug 2012, 01:09
dpvtank wrote:
noboru wrote:
In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles from clinging to their shells. When fully grown, however, the crabs can readily withstand tidal currents without burrowing, and thus they acquire substantial populations of barnacles. Surprisingly, in areas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow.

Which of the following, if true, most helps to explain the surprising finding?

(A) Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs.
(B) Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.
(C) The strength of the tidal currents in a given location varies widely over the course of a day.
(D) A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.
(E) Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.

I had a really hard time understanding Choice A. I'm wondering if my thought process is correct in disqualifying A now.

Here's how I understand the argument:
- high tidal waves --> more burrowing for juvenile horseshoe crabs --> decreased barnacles
BUT ALSO
- low tidal waves --> less burrowing for juvenile horseshoe crabs --> decreased barnacles
how can this be?

A. Tells us that the water tides don't matter. So the less or more barnacle populations have to do with burrowing then (given the premises). So we are left with the situation where:
- more burrowing --> less barnacle population
- less burrowing --> less barnacle population

Is this accurate?

Let me take a dig at trying to explain the answer choice.

Choice A says that the tidal ways do not dislodge the barnacles from the crab-shells. Thus high or low tidal waves should not make a difference in the population of barnacles, instead burrowing should make all the difference i.e. less burrowing = more barnacles and vice-versa.

Hence in low tidal waves areas the juvenile crabs would burrow less hence ideally the population of barnacles on the juvenile crabs should be larger. However this is contrary to the observed phenomenon i.e. in low tidal areas the barnacle population on juvenile crabs was not found to be larger. Thus option A does not help us resolve the paradox. Hence A can be eliminated.

Hope this helps.
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Re: In order to withstand tidal currents, juvenile horseshoe [#permalink]

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07 Oct 2012, 04:47
I also selected E as the answer but i have a small doubt . what if the there are fully grown crabs in the weak tidal current area also , then choice e would not hold true because according to the answer choice fully grown crabs won't shed their shells. also in the premise the fully grown crabs have the maximum barnicles. do we have to assume that the weak tidal area do not have a substantial population of fully grown crabs ?
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Re: In order to withstand tidal currents, juvenile horseshoe [#permalink]

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07 Oct 2012, 23:27
In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles from clinging to their shells. When fully grown, however, the crabs can readily withstand tidal currents without burrowing, and thus they acquire substantial populations of barnacles. Surprisingly, in areas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow.

Which of the following, if true, most helps to explain the surprising finding?

(A) Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs.
(B) Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.
(C) The strength of the tidal currents in a given location varies widely over the course of a day.
(D) A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.
(E) Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.

This is more of a resolve the paradox question. Here E gives us a clear explanation of why the finding is surprised.
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Re: In order to withstand tidal currents, juvenile horseshoe [#permalink]

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29 Apr 2013, 06:15
The paradox is about the juvenile crabs only. Information about Adults is given to highlight that tidal currents causes juveniles to burrow --> burrowing leads to shedding of barnacle population. Essentially, the argument attributes the lack of barnacle population on juvenile crabs to the act of burrowing.

However, there is a paradox because even in weak tidal current areas where burrowing does not happen, the lack of barnacle population on juvenile crabs is observed.

How to resolve the paradox? By attributing the lack of barnacle population on juvenile crabs to something else than the tidal currents. Choice E solves that. If there is some other reason than what is assumed, then the paradox is solved!
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Re: In order to withstand tidal currents, juvenile horseshoe [#permalink]

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14 Jun 2015, 07:16
My 2 cents:

In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles from clinging to their shells.
When fully grown, however, the crabs can readily withstand tidal currents without burrowing, and thus they acquire substantial populations of barnacles.
Surprisingly, in areas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow.

Which of the following, if true, most helps to explain the surprising finding?
(A) Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs.
>>Evident from argument "burrowing discourages barnacles from clinging". Doesn't help in answering the paradox.
(B) Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.
>>But juvenile horseshoe crabs are found not to have significant barnacle populations in such areas. Doesn't help.
(C) The strength of the tidal currents in a given location varies widely over the course of a day.
>> I found this one intriguing. but this means Barnacle population shouldnt vary much because of variation in tidal strength.
(D) A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.
>>Irrelevant.
(E) Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.
>>Now apart from sand borrowing this is anther reason for low barnacle population. This answers bth part of argument.
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In order to withstand tidal currents, juvenile horseshoe [#permalink]

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17 Jun 2015, 14:13
In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles from clinging to their shells. When fully grown, however, the crabs can readily withstand tidal currents without burrowing, and thus they acquire substantial populations of barnacles. Surprisingly, in areas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow.

Which of the following, if true, most helps to explain the surprising finding?

The question to answer is, why do juvenile horseshoe crabs have sparse barnacle populations although they aren't burrowing (Burrowing decreases barnacle accumulation)?

(A) Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs. doesn't answer the question
(B) Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest. This would have the opposite effect.
(C) The strength of the tidal currents in a given location varies widely over the course of a day. not relevant to our question
(D) A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food. also out of scope
(E) Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year. This explains why they don't have barnacles although we would think they would because they don't burrow. They shed the barnacles along with their shells.
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In order to withstand tidal currents, juvenile horseshoe [#permalink]

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07 Sep 2016, 08:49
Hi guys,

Pardon me for bring up this post.

I am quite not satisfied with E. This is my reasoning why:
(E) Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.
The passage states that "Surprisingly, inareas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow."

So, in E,the crab is mature and thus can shed its shell; but in the quoted above, the crab is just a kid, this mean it can not shed its shell. The choice turns out irrelevant, or at least can not explain the paradox (to me, of course). So I eliminated E.
IMO, If something can fill the gap between the quoted and E, states or implies, it is "juvenile crab is fully grown". Is it correct?

Could somebody point out the flaw in my reasoning? Thanks in advance.
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Re: In order to withstand tidal currents, juvenile horseshoe [#permalink]

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30 Jan 2017, 09:06
ThangLe wrote:
Hi guys,

Pardon me for bring up this post.

I am quite not satisfied with E. This is my reasoning why:
(E) Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.
The passage states that "Surprisingly, inareas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow."

So, in E,the crab is mature and thus can shed its shell; but in the quoted above, the crab is just a kid, this mean it can not shed its shell. The choice turns out irrelevant, or at least can not explain the paradox (to me, of course). So I eliminated E.
IMO, If something can fill the gap between the quoted and E, states or implies, it is "juvenile crab is fully grown". Is it correct?

Could somebody point out the flaw in my reasoning? Thanks in advance.

Option E states that the juvenile crabs will have shedded its shells several times by the time it reaches its maturity.
Re: In order to withstand tidal currents, juvenile horseshoe   [#permalink] 30 Jan 2017, 09:06

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