On Pacific islands, a newly arrived gecko species, the house

Question

On Pacific islands, a newly arrived gecko species, the house gecko, is displacing the previously established mourning gecko in urban areas, but populations of the two species are more stable in rural areas far from human settlement. The house gecko does not attack the mourning gecko, but in areas where insects congregate it prevents the mourning gecko from feeding on them.

Which of the following contributes most to an explanation of the difference between gecko populations in urban and rural areas?

A. In urban areas, geckos are valued because they eat so many insects.

B. Geckos defend territories against other members of the same species.

C. House geckos that arrive on islands are carried there in boats and planes.

D. places where there are lighted buildings, insects tend to gather around the light.

E. Mourning geckos are all females and reproduce asexually, but house geckos reproduce sexually.

pqhai · Accepted Answer

ANALYZE THE STIMULUS:

Fact:  A newly arrived gecko species, the house gecko, is displacing the previously established mourning gecko in urban areas, 
 Fact:  But populations of the two species are more stable in rural areas far from human settlement. 
 Fact:  The house gecko  does not attack  the mourning gecko, but in areas where insects congregate it  prevents the mourning gecko from feeding  on them.

KEY POINT is: competing for food (insect) ==> difference in populations.

ANALYZE EACH ANSWER:

A. In urban areas, geckos are valued because they eat so many insects. 
 Wrong.  Does not explain the difference between populations of the two geckos in urban and rural areas.

B. Geckos defend territories against other members of the same species. 
 Wrong.  Same as A.

C. House geckos that arrive on islands are carried there in boats and planes. 
 Wrong.  Same as A

D. places where there are lighted buildings, insects tend to gather around the light. 
  Correct.    Because the two geckos have same eating habit, they eat insect. In rural areas, because of few lights, the food – “insect populations” is spread,  the two geckos seem to have same opportunity to access the food source  ( Remember fact#3: house gecko does NOT attack mourning gecko ). ==> The two geckos' populations seem to be the same in rural areas. 
However, in urban areas, insects gather around the light, the the “stronger” gecko will defeat the “weaker” one to get food – insect. That makes the population of house gecko in urban areas is larger the that of mourning gecko.

E. Mourning geckos are all females and reproduce asexually, but house geckos reproduce sexually.
 Wrong.  Does not help. The main point is “competing for food ==> difference in population”

Hope it helps

SimaQ · Answer

I pick D

House gecko prevents mourning gecko from feeding in areas whre insects congregate: Thus if insects tend to congregate near the ligth it is logical to assume that in urban areas mourning gecko has a hard time getting something to eat...

fozzzy · Answer

Can someone provide a detailed analysis on this question. Thanks!

Zarrolou · Answer

FACT 1: The house gecko is displacing the previously established mourning gecko in urban areas
Populations of the two species are more stable in rural areas far from human settlement.

FACT 2: The house gecko prevents the mourning gecko from feeding on insects.

The correct answer will link the two fact, will be something that show a difference between the two areas.

How they reproduce, how they arrived on the island, why they are valued are all out of scope.

A. In urban areas, geckos are valued because they eat so many insects.
C. House geckos that arrive on islands are carried there in boats and planes.
E. Mourning geckos are all females and reproduce asexually, but house geckos reproduce sexually.

The real contenders IMO are B and D. 
 B. Geckos defend territories against other members of the same species. 
This is not actually a difference between the two areas (it is not specified where this happens) and moreover it does not link fact 1 and fact 2.
 D. places where there are lighted buildings, insects tend to gather around the light. 
where there are lighted buildings ( URBAN AREAS ) insects tend to gather around the light + FACT 2: The house gecko prevents the mourning gecko from feeding on insects.  =>  FACT 1 .

killthegmatavi · Answer

Answer: Explanation to the difference between gecko population in urban and rural areas.
Need to explain why there is a difference between gecko population in urban and rural areas

Conclusion: house gecko is displacing the previously established morning gecko in urban areas.
Premise: Areas where insects congregate it prevents the mourning gecko from feeding on them.
So if it is proved that this congregation takes place only in urban areas than it gives an explanation or reason for the difference between gecko population in urban areas only
a. wrong. no difference between house and morning gecko.
b. wrong
c. wrong
d. correct: mentioned that two species are more stable in rural areas far from human settlement
rural settlement is the area which is far from human settlement. hence if the congregation of insects take plan in lighted building(urban areas) than it gives an explanation for the given difference. At the lighted building(urban areas) house gecko prevents mourning gecko from feeding on them, which eventually leads to reduced population of mourning gecko.
e. wrong

kinjiGC · Answer

On Pacific islands, a newly arrived gecko species, the house gecko, is displacing the previously established mourning gecko in urban areas, but populations of the two species are more stable in rural areas far from human settlement. The house gecko does not attack the mourning gecko, but in areas where insects congregate it prevents the mourning gecko from feeding on them.

Which of the following contributes most to an explanation of the difference between gecko populations in urban and rural areas?

The Congregation of the insects happens in Urban area and doesn't happen the rural areas.

We need to find the reason for that difference

A. In urban areas, geckos are valued because they eat so many insects  -> This option doesn't talk about congregation

B. Geckos defend territories against other members of the same species  -> Doesn't talk about difference in Urban and rural areas

C. House geckos that arrive on islands are carried there in boats and planes ->  Out of scope

D. places where there are lighted buildings, insects tend to gather around the light.  -> Provides a reason for the congregation -> Correct

E. Mourning geckos are all females and reproduce asexually, but house geckos reproduce sexually  -> We are not talking about reproduction types here

apoorv601 · Answer

D
Conclusion - the house gecko, is displacing the previously established mourning gecko in urban areas and not in rural areas. 
Premise - The house gecko does not attack the mourning gecko, but in areas where insects congregate it prevents the mourning gecko from feeding on them.
Thus one can pre-think that the conclusion is true because the urban area has more areas where inspects congregate
D specifies one such area

manhasnoname · Answer

Where does the passage indicate that urban areas have lighted buildings and rural areas don't?

Should the test taker impart his/her outside knowledge to answer this question?

sayantanc2k · Answer

Yes this kind of small  leap  is acceptable in GMAT. That urban areas have more lighted buildings than rural areas is a basic knowledge that is alright to use.

anairamitch1804 · Answer

The question asks to identify an option that contributes most to an explanation of the difference between gecko populations in urban and rural areas.

In rural areas ---> no lighted buildings ---> no gathering (congregation) of insects around lights ---> House gecko not stopping Mourning gecko feeding on insects ---> probably no starving of Mourning gecko ---> stable population

In urban areas ---> lighted buildings ---> gathering (congregation) of insects around lights ---> House gecko stopping Mourning gecko feeding on insects ---> probably starving of Mourning gecko ---> reducing Mourning gecko population after introduction of House gecko.

Hence D.

KarishmaB · Answer

Two gecko species - house gecko and mourning gecko

Urban areas - House gecko displacing mourning gecko
Rural areas (far from humans) - Both species stable

In areas where insects congregate house gecko prevents the mourning gecko from feeding on them.

We know something abt the diff between the two - where insects congregate, house geckos prevail. 
So now we need an explanation about why house geckos prevail in urban areas but not in rural. Do insects congregate in urban areas? Why?

A. In urban areas, geckos are valued because they eat so many insects.

Geckos (all types) are valued because they eat insects. So apparently, humans do not threaten geckos. Why is there is diff in the population of the two species of geckos? Doesn't say.

B. Geckos defend territories against other members of the same species.

Tells you that they defend territories against members of SAME species. We don't know why house gecko is replacing mourning gecko in urban but not in rural.

C. House geckos that arrive on islands are carried there in boats and planes.

Doesn't matter how they came to the island. We need an explanation on why one is replacing the other in urban areas but to in rural areas.

D. places where there are lighted buildings, insects tend to gather around the light.

Correct. Urban areas have lighted buildings so insects will congregate there. Then house geckos will prevail and mourning geckos will not get food. Rural areas (far away from humans) will not have lighted buildings and hence no congregation of insects. Hence both will survive. This explains the difference.

E. Mourning geckos are all females and reproduce asexually, but house geckos reproduce sexually.

Doesn't explain the difference between urban and rural settings.

Answer (D)

Nina1987 · Answer

GMATNinja ,  ThatDudeKnows ,  DmitryFarber ,  GMATNinjaTwo ,  IanStewart ,  MartyTargetTestPrep ,  RonPurewal ,  KarishmaB ,  MarkSullivan ,  AjiteshArun ,  EMPOWERgmatRichC ,  mikemcgarry ,  sayantanc2k ,  TommyWallach

is it alright to bring in the assumption that urban areas are more lit than rural ones? or this question is an exception? Thanks

IanStewart · Answer

The stem specifically talks about rural areas "far from human settlement", and it's safe to infer from that phrase that there aren't many buildings with lights in those areas.

Blackcrow1972 · Answer

Option D
This directly links urban areas (with lighted buildings) to higher insect concentrations. Since house geckos outcompete mourning geckos in areas where insects congregate, this provides a clear explanation for why the house gecko displaces the mourning gecko in urban areas but not in rural areas. Relevant and logical.

MS61 · Answer

A. In urban areas, geckos are valued because they eat so many insects.-  Incorrect : Valued?

B. Geckos defend territories against other members of the same species. -  Incorrect: other members of same species ? Given that they are displacing

C. House geckos that arrive on islands are carried there in boats and planes. -  Incorrect: how the arrive is irrelevant

D. places where there are lighted buildings, insects tend to gather around the light. -  Correct: Lighted buildings = Urban, hence more activity and displacement

E. Mourning geckos are all females and reproduce asexually, but house geckos reproduce sexually -  Incorrect: Irrelevant

On Pacific islands, a newly arrived gecko species, the house

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On Pacific islands, a newly arrived gecko species, the house

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