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When mercury-vapor streetlights are used in areas inhabited by insect

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When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 28 Nov 2015, 15:34
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Which of the following most logically completes the argument below?

When mercury-vapor streetlights are used in areas inhabited by insect-eating bats, the bats feed almost exclusively around the lights, because the lights attract flying insects. In Greenville, the mercury-vapor streetlights are about to be replaced with energy-saving sodium streetlights, which do not attract insects. This change is likely to result in a drop in the population of insect-eating bats in Greenville, since __________.

(A) the bats do not begin to hunt until after sundown

(B) the bats are unlikely to feed on insects that do not fly

(C) the highway department will be able to replace mercury-vapor streetlights with sodium streetlights within a relatively short time and without disrupting the continuity of lighting at the locations of the streetlights

(D) in the absence of local concentrations of the flying insects on which bats feed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat

(E) bats use echolocation to catch insects and therefore gain no advantage from the fact that insects flying in the vicinity of streetlights are visible at night
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 29 Nov 2015, 07:34
Steinbeck wrote:
Which of the following most logically completes the argument below?

When mercury-vapor streetlights are used in areas inhabited by insect-eating bats, the bats feed almost exclusively around the lights, because the lights attract flying insects. In Greenville, the mercury-vapor streetlights are about to be replaced with energy-saving sodium streetlights, which do not attract insects. This change is likely to result in a drop in the population of insect-eating bats in Greenville, since ___________________________________

(A) the bats do not begin to hunt until after sundown
(B) the bats are unlikely to feed on insects that do not fly
(C) the highway department will be able to replace mercury-vapor streetlights with sodium streetlights within a relatively short time and without disrupting the continuity of lighting at the locations of the streetlights
(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat
(E) bats use echolocation to catch insects and therefore gain no advantage from the fact that insects flying in the vicinity of streetlights are visible at night


Mercury-vapor streetlights----> Attracts insects -----> Bats prey on them around the lights (at a single location)

No Mercury-vapor streetlights -----> No insects around the lights -------> Drop in population of bats

So, how does Bats survive ? Does they stop eating insects ? Probably not , they must be hunting the insects anyway for survival.



(A) the bats do not begin to hunt until after sundown - Talks about sundown , but doesn't account for the Bats food and reduced population.

(B) the bats are unlikely to feed on insects that do not fly - Out of scope.

(C) the highway department will be able to replace mercury-vapor streetlights with sodium streetlights within a relatively short time and without disrupting the continuity of lighting at the locations of the streetlights - Talks about replacement of llights and not about the reduction in population of bats.

(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat - This can be a cuse for reduction of Bats population.

(E) bats use echolocation to catch insects and therefore gain no advantage from the fact that insects flying in the vicinity of streetlights are visible at night - Out of scope.

Hence answer is (D)
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 22 Dec 2015, 15:37
Steinbeck wrote:
Which of the following most logically completes the argument below?

When mercury-vapor streetlights are used in areas inhabited by insect-eating bats, the bats feed almost exclusively around the lights, because the lights attract flying insects. In Greenville, the mercury-vapor streetlights are about to be replaced with energy-saving sodium streetlights, which do not attract insects. This change is likely to result in a drop in the population of insect-eating bats in Greenville, since ___________________________________

(A) the bats do not begin to hunt until after sundown
(B) the bats are unlikely to feed on insects that do not fly
(C) the highway department will be able to replace mercury-vapor streetlights with sodium streetlights within a relatively short time and without disrupting the continuity of lighting at the locations of the streetlights
(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat
(E) bats use echolocation to catch insects and therefore gain no advantage from the fact that insects flying in the vicinity of streetlights are visible at night

We need to find an explanation why population of bats will decline
A is wrong since time of hunt is not a factor. What if bats begin after sundown? It doesn't explain why population will decline
B is wrong since it doesn't explain why population will decline (only says what kind of insects bats prey on)
C is out of scope
D is correct. If bats spend more energy and require much larger quantities of insects to sustain each bat then the same number of insects will be available for fewer bats (competiton increases=))
E is out of scope
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 26 Jan 2016, 21:21
according to the OG online results screen, this Q is a Medium difficulty level. Please update to reflect
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 29 Apr 2016, 05:22
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Keats wrote:
Which of the following most logically completes the argument below?

When mercury-vapor streetlights are used in areas inhabited by insect-eating bats, the bats feed almost exclusively around the lights, because the lights attract flying insects. In Greenville, the mercury-vapor streetlights are about to be replaced with energy-saving sodium streetlights, which do not attract insects. This change is likely to result in a drop in the population of insect-eating bats in Greenville, since ___________________________________

(A) the bats do not begin to hunt until after sundown
(B) the bats are unlikely to feed on insects that do not fly
(C) the highway department will be able to replace mercury-vapor streetlights with sodium streetlights within a relatively short time and without disrupting the continuity of lighting at the locations of the streetlights
(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat
(E) bats use echolocation to catch insects and therefore gain no advantage from the fact that insects flying in the vicinity of streetlights are visible at night


Respoding to a PM,

lets see the PARA-
Bats feed EXCLUSIVELY on the insects around the street light. These street lights are now being converted to some other form which does not attract light.
The conclusion is "This change is likely to result in a drop in the population of insect-eating bats" and we have to complete the statement citing some reason for it..


What are you required to do- Give reasons for the conclusion..

What does it ask you to do?
Your answer has to be -
1) firstly related to some info existing in the PARA.
2) secondly it has to be strengthening the conclusion.


lets see the choices for these two points-

(A) the bats do not begin to hunt until after sundown
Does it give reason to strengthen our conclusion. NO..

(B) the bats are unlikely to feed on insects that do not fly
Again nothing .. the point would be same for any kind of street lights..

(C) the highway department will be able to replace mercury-vapor streetlights with sodium streetlights within a relatively short time and without disrupting the continuity of lighting at the locations of the streetlights
It does not follow any of our 2 points
Out of context


(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat
Now this is related to change over of lights..
Also that word in capitals EXCLUSIVELY tells us that they were having easy meals. But this changeover has resulted in two things-
a) Lesser avail of insects in close proximity
b) spending extr aenergy for food and in turn requiring MORE food. likely that the strength will go down
PERFECT as an answer


(E) bats use echolocation to catch insects and therefore gain no advantage from the fact that insects flying in the vicinity of streetlights are visible at night
again Not related to the conclusion
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 12 May 2016, 23:14
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When Mercury vapor street lights were used - Bats fed insect around the light
Mercury vapor streetlights are now replaced by sodium streetlights - Does not attract insects - Bats population will drop

We have to select an answer choice that will provide the reason for the drop in bat population

(A) the bats do not begin to hunt until after sundown - Incorrect - Irrelevant

(B) the bats are unlikely to feed on insects that do not fly - Incorrect - Rather than providing the reason for the decline in bat population this option tries to attack the fact stated in the argument.

(C) the highway department will be able to replace mercury-vapor streetlights with sodium streetlights within a relatively short time and without disrupting the continuity of lighting at the locations of the streetlights - Incorrect - Irrelevant

(D) in the absence of local concentrations of the flying insects on which bats feed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat - Correct - Suppose there were 100 bats and 100 insects, earlier 1 bat required 1 insect. Because the light does not attract insects bats spend more energy now. So 1 bat requires 2 insects. 100 insects is sufficient for only 50 bats. Other 50 will starve to death, resulting in population decline.

(E) bats use echolocation to catch insects and therefore gain no advantage from the fact that insects flying in the vicinity of streetlights are visible at night - Incorrect - Again attacks the fact stated in the argument

Answer: D
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 14 Mar 2017, 15:16
Strenghten question: we are looking for answe that will tell us about the bats population at risk connected with the lights replacements

D is the one that fits
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 18 Aug 2017, 03:22
Correct choice is 'D' - Since there will be no local concentrations of flying insects around Greenville streetlights after the change, the bats will most likely have more trouble getting enough to eat, and that their local population will therefore fall.
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 13 Mar 2018, 10:01
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Why isn't A the answer? If the bats only hunt after sundown, and exclusively feed on flying insects, they won't be able to catch them under the lights, and hence starve and die?

is it that the GMAT assumes bats are nocturnal, and will be able to hunt the insects regardless of whether the insects gather around streetlights or not?
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 10 Apr 2018, 06:17
Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn,
sayantanc2
VeritasPrepKarishma

First, i view this question as an assumption questions. so i need get a unstated premise that author believe it can lead to the conclusion.
i don't understand how D leads to the conclusion, i think i must miss something.
D says, in the area where lack the concentration of flying insects, bats need to spend more energy to hunt,
here is the question, how bats spend more energy will lead to drop population.
more energy means it is harder for bats to hunt, but they highly possible to stay in Greeville, then the population does not necessary drop,

Please help point out.
Have a nice day
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 10 Apr 2018, 16:25
zoezhuyan wrote:
Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn,
sayantanc2
VeritasPrepKarishma

First, i view this question as an assumption questions. so i need get a unstated premise that author believe it can lead to the conclusion.
i don't understand how D leads to the conclusion, i think i must miss something.
D says, in the area where lack the concentration of flying insects, bats need to spend more energy to hunt,
here is the question, how bats spend more energy will lead to drop population.
more energy means it is harder for bats to hunt, but they highly possible to stay in Greeville, then the population does not necessary drop,

Please help point out.
Have a nice day
>_~

Hi zoezhuyan!

Happy to help :-) The idea here is that with the old lights, there are lots of insects in one place (near the lights). That makes it really easy for bats to find food -- all they have to do is go to the lights, and they will find lots of insects to eat. With the new lights, the insects will be spread out all over the place. That means that it will be harder for the bats to find insects to eat, since now they have to fly around and look much harder for the insects. That means the population of bats will drop, since it's harder for them to find food.

Does that make sense? If not, let me know :-)
-Carolyn
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 11 Apr 2018, 00:07
MagooshExpert wrote:
Hi zoezhuyan!

Happy to help :-) The idea here is that with the old lights, there are lots of insects in one place (near the lights). That makes it really easy for bats to find food -- all they have to do is go to the lights, and they will find lots of insects to eat. With the new lights, the insects will be spread out all over the place. That means that it will be harder for the bats to find insects to eat, since now they have to fly around and look much harder for the insects. That means the population of bats will drop, since it's harder for them to find food.

Does that make sense? If not, let me know :-)
-Carolyn


Thanks for your explanation, MagooshExpert Carollyn,
I doubt i misunderstand the idenfification of assumption -- An assumption is unstated something that the author must believe to be true in order to draw a certain conclusion.

based on the assumption, the author must conclude the conclusion, right?
an example from Mahantta guide 6:
No athletes under the age of 14 can qualify for Country Y's Olympic team, Therefore, Adrienne can't qualify for Country Y's Olympic.
The assumption is Adrienne is an athlete from Country Y who is under the age of 14.
Apparently, the author must can conclude Adrienne can't qualify for Country Y's Olympic.

In this case, I am not clear why D can lead to the conclusion,
although it is much harder for bats to hunt insects, but it does not necessary conclude the population of bats will drop.
It is highly possible that the population of bats won't drop.

Please help clarify.
Thanks in advance

Have a nice day
>_~
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 16 Apr 2018, 10:57
zoezhuyan wrote:
Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn,
sayantanc2
VeritasPrepKarishma
First, i view this question as an assumption questions. so i need get a unstated premise that author believe it can lead to the conclusion.
i don't understand how D leads to the conclusion, i think i must miss something.
D says, in the area where lack the concentration of flying insects, bats need to spend more energy to hunt,
here is the question, how bats spend more energy will lead to drop population.
more energy means it is harder for bats to hunt, but they highly possible to stay in Greeville, then the population does not necessary drop,

Please help point out.
Have a nice day
>_~

I know that I'm late to the party, but let's see if this helps at all:

Quote:
(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat

Choice (D) specifically tells us that when bats expend more energy on hunting for food, much larger quantities of insects are required to sustain each bat. In other words, the bats will need more energy, so they will need to eat more insects. But the number of insects is not expected to change. The current insect level is enough to feed the current bat population. If the size of both populations remains the same but the number of insects required per bat increases, then some of the bats will not have enough insects to eat. Thus, some of the bats will not survive, and the bat population will likely drop.
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 17 Apr 2018, 05:09
GMATNinja wrote:
zoezhuyan wrote:
Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn,
sayantanc2
VeritasPrepKarishma
First, i view this question as an assumption questions. so i need get a unstated premise that author believe it can lead to the conclusion.
i don't understand how D leads to the conclusion, i think i must miss something.
D says, in the area where lack the concentration of flying insects, bats need to spend more energy to hunt,
here is the question, how bats spend more energy will lead to drop population.
more energy means it is harder for bats to hunt, but they highly possible to stay in Greeville, then the population does not necessary drop,

Please help point out.
Have a nice day
>_~

I know that I'm late to the party, but let's see if this helps at all:

Quote:
(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat

Choice (D) specifically tells us that when bats expend more energy on hunting for food, much larger quantities of insects are required to sustain each bat. In other words, the bats will need more energy, so they will need to eat more insects. But the number of insects is not expected to change. The current insect level is enough to feed the current bat population. If the size of both populations remains the same but the number of insects required per bat increases, then some of the bats will not have enough insects to eat. Thus, some of the bats will not survive, and the bat population will likely drop.



Hi GMATNinja, I can understand what you explanation,
i have one more question, how can i get the information The current insect level is enough to feed the current bat population.

Would you please clarify further?

Have a nice day
>_~
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 10 May 2018, 10:08
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We are just given that special types of bats feed ALMOST EXCLUSIVELY on insects present in areas around the light. How did we link FEEDING on insects to one of such extreme assumption of NOT SURVIVING without feeding on insects as in OA?
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When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 10 May 2018, 10:49
Here is my explanation, just read this "bats feed almost exclusively arount the light" why ? :)

Because bats consume much more energy on flying to and fro :) so these bats think why should we run up and down the town in search of insects that are spread all around the town (meaning the concentration of insects is not dense compared to the place lit by mercury-vapor streetlights. So these bats for sure choose places with high concentration of insects such as the one around mercury lights, and thus these bats are always happy :) consume less energy, eat well :) but once these lights are replaced with street lights, the insects will start flying all around town area of which say is 10000 sq km :) (thus concentration of insects around ex mercury place gets sparse)

hence being angry and frustrated, bats wont have choice but to chase the insects, flying all around town :) thus they will consume more energy on flying tens of kilometrs to catch insects , and it will cause a drop in a number of bats :) :)
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 11 May 2018, 13:32
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adkikani wrote:
GMATNinja VeritasPrepKarishma

We are just given that special types of bats feed ALMOST EXCLUSIVELY on insects present in areas around the light. How did we link FEEDING on insects to one of such extreme assumption of NOT SURVIVING without feeding on insects as in OA?

Thanks dave13 for the explanation!

Also, keep in mind that the conclusion is that "this change is likely to result in a drop in the population." We do not need something that PROVES that the population will drop. As explained perfectly by dave13, choice (D) tells us why the change will LIKELY result in a drop in the bat population.

zoezhuyan wrote:
GMATNinja wrote:
zoezhuyan wrote:
Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn,
sayantanc2
VeritasPrepKarishma
First, i view this question as an assumption questions. so i need get a unstated premise that author believe it can lead to the conclusion.
i don't understand how D leads to the conclusion, i think i must miss something.
D says, in the area where lack the concentration of flying insects, bats need to spend more energy to hunt,
here is the question, how bats spend more energy will lead to drop population.
more energy means it is harder for bats to hunt, but they highly possible to stay in Greeville, then the population does not necessary drop,

Please help point out.
Have a nice day
>_~

I know that I'm late to the party, but let's see if this helps at all:

Quote:
(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat

Choice (D) specifically tells us that when bats expend more energy on hunting for food, much larger quantities of insects are required to sustain each bat. In other words, the bats will need more energy, so they will need to eat more insects. But the number of insects is not expected to change. The current insect level is enough to feed the current bat population. If the size of both populations remains the same but the number of insects required per bat increases, then some of the bats will not have enough insects to eat. Thus, some of the bats will not survive, and the bat population will likely drop.



Hi GMATNinja, I can understand what you explanation,
i have one more question, how can i get the information The current insect level is enough to feed the current bat population.

Would you please clarify further?

Have a nice day
>_~

zoezhuyan, sorry for the delay...

Regarding the portion you highlighted, I was simply referring to the pre-change bat population level. Regardless of what that level is, we can say that there are currently enough insects to sustain the current population level. Assuming that nothing changes, the status quo will remain the same. But if bats suddenly need more energy (as explained by dave13), then there might not be enough insects to meet the increased demand for food.

I hope that helps!
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 02 Jun 2018, 00:57
Question Stem:-

In Greenville, the mercury-vapor streetlights are about to be replaced with energy-saving sodium streetlights, which do not attract insects.

Conclusion:-

This change is likely to result in a drop in the population of insect-eating bats in Greenville, since __________.

Reason:-

mercury-vapor streetlights lights attract flying insects leading to concentrations of the flying insects around the mercury-vapor streetlights. If mercury-vapor streetlights are about to be replaced with energy-saving sodium streetlights, which do not attract insects then concentrations of the flying insects will not be available for insect-eating bats to feed on. If an alternate is not provided then this is likely to result in a drop in the population of insect-eating bats.

Option D is correct because it clarifies this point, "in the absence of local concentrations of the flying insects on which bats feed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat"
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 02 Jun 2018, 01:10
GMATNinja wrote:
zoezhuyan wrote:
Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn,
sayantanc2
VeritasPrepKarishma
First, i view this question as an assumption questions. so i need get a unstated premise that author believe it can lead to the conclusion.
i don't understand how D leads to the conclusion, i think i must miss something.
D says, in the area where lack the concentration of flying insects, bats need to spend more energy to hunt,
here is the question, how bats spend more energy will lead to drop population.
more energy means it is harder for bats to hunt, but they highly possible to stay in Greeville, then the population does not necessary drop,

Please help point out.
Have a nice day
>_~

I know that I'm late to the party, but let's see if this helps at all:

Quote:
(D) in the absence of local concentrations of the flying insects on which bats teed, the bats expend much more energy on hunting for food, requiring much larger quantities of insects to sustain each bat

Choice (D) specifically tells us that when bats expend more energy on hunting for food, much larger quantities of insects are required to sustain each bat. In other words, the bats will need more energy, so they will need to eat more insects. But the number of insects is not expected to change. The current insect level is enough to feed the current bat population. If the size of both populations remains the same but the number of insects required per bat increases, then some of the bats will not have enough insects to eat. Thus, some of the bats will not survive, and the bat population will likely drop.


GMATNinja - I feel the logic is related to non availability of flying insects in concentrations rather than pre & post change in insect population? The passage is silent on whether the insect population is sufficient or about their reproduction rates? Please clarify.
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Re: When mercury-vapor streetlights are used in areas inhabited by insect  [#permalink]

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New post 02 Jun 2018, 06:14
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Hi CAMANISHPARMAR

You asked me to weigh in on this one so I will give you my thoughts. There are already some great explanations above.

Basically, we are looking for something that describes why replacing these lights is going to be a BIG PROBLEM for the bats.
It needs to be a life-threatening problem, because the argument says the change will likely result in a population decline. Population decline means existing bats die off and/or the next generations of bats are smaller.

What could cause such a thing?
Hmm, 2 big categories come to mind: a shortage of any of the essentials a bat needs to survive (food, nesting grounds, etc), or the presence of a killer such as a disease or a predator. (A natural disaster would be another option, though I don't foresee that coming into play here.)

So I could go for any answer that gives me a shortage of essentials or the presence of a killer.

For best results, we have this all in mind BEFORE we go shopping through the answer choices for an answer that meets our needs.

No answer choices give us a killer. And only one of our answer choices could lead to a shortage of essentials. D describes that bats are going to be working way harder than before to find enough food to eat, and as a result, they're going to suddenly need more food. If they can't find that additional food, they will die ... and/or not be able to feed the same number of baby bats as before, thus reducing the next generation.

It is not 100% sure that they won't be able to find additional food, but as GMATNinja and dave13 have mentioned, 1) we don't have to be 100% sure (the question says "likely"), and 2) there is a finite existing insect population. It's reasonable to envision that there will not be enough insects to feed the bats' increased appetite.

Let me know if this helps.
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Re: When mercury-vapor streetlights are used in areas inhabited by insect &nbs [#permalink] 02 Jun 2018, 06:14

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