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# The Laysan Rail, an insectivore bird once present on several of the Ha

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The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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05 Jan 2019, 07:46
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The Laysan Rail, an insectivore bird once present on several of the Hawaiian Islands, can no longer be found and is thought to be extinct. Scientists originally thought that a decrease in the amount of ground vegetation available for nesting was responsible for the decline of the bird. However, they now believe that increased competition for food was ultimately responsible for the Laysan Rail's inability to survive.

Which of the following would best help to account for the change in the accepted explanation for the Laysan Rail's extinction?

A. The vegetation on the Laysan Rail's home island was decimated when rabbits were introduced to the island in the 1910s.

B. When attempts were made to relocate the Laysan Rail to other islands, the birds lost the geographical cues that they relied on for finding mating sites.

C. The Laysan Rail builds nests under dense ground cover to protect the eggs.

D. An increase in the use of pesticides resulted in a decrease in the numbers of flies and moths present in the Laysan Rails territory.

E. Many species nested.in the same types of vegetation as the Laysan Rail.

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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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08 Jan 2019, 18:22
The question asks indirectly to find a reason for extinction except for lack of green vegetation.
If we take this into consideration only D option attacks the question.
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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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08 Jan 2019, 20:15
Answer E supports that there is increase in competition.

Answer D needs assumption that the bird's food is flies and moths. Decrease in these food sources necessitate the bird to migrate, starve to death, or even seek other types of food.
The other assumption is that when seeking other food sources, the bird is not able to compete with others.

So, I choose E that requires fewer assumptions - assumption that some species share the same food sources.

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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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08 Jan 2019, 20:37
Valhalla wrote:
Answer E supports that there is increase in competition.

Answer D needs assumption that the bird's food is flies and moths. Decrease in these food sources necessitate the bird to migrate, starve to death, or even seek other types of food.
The other assumption is that when seeking other food sources, the bird is not able to compete with others.

So, I choose E that requires fewer assumptions - assumption that some species share the same food sources.

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Valhalla Option E does not mention green vegetation as food source. It talks about vegetation being nesting ground. So E does not even touch the topic of competition for food source.

But we need the answer choice to throw some light regarding competition for food source as the question asks us to look for a statement which helps to account for the change in the accepted explanation for the Laysan Rail's extinction.
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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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08 Jan 2019, 21:52
I think E is d best answer.

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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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09 Jan 2019, 00:11
Urgent expert help needed here pls...i marked D) because it was the only option in the scope though it dint make any sense at all to mark it

Argument clearly says “competition for food lead to decline” .D says competition for food exists.How can it be correct..?

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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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09 Jan 2019, 21:09
redskull1 wrote:
Urgent expert help needed here pls...i marked D) because it was the only option in the scope though it dint make any sense at all to mark it

Argument clearly says “competition for food lead to decline” .D says competition for food exists.How can it be correct..?

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The question states that competition for food was responsible for extinction. And option D gives us one possible way of how competition existed for food.
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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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10 Jan 2019, 01:18
Can someone please explain this question in detail?
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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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10 Jan 2019, 01:32
Just to add....how that competition was brought about is also irrelevant to the argument in D).Would really love some expert analysis...

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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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11 Jan 2019, 10:39
Bunuel wrote:
The Laysan Rail, an insectivore bird once present on several of the Hawaiian Islands, can no longer be found and is thought to be extinct. Scientists originally thought that a decrease in the amount of ground vegetation available for nesting was responsible for the decline of the bird. However, they now believe that increased competition for food was ultimately responsible for the Laysan Rail's inability to survive.

Which of the following would best help to account for the change in the accepted explanation for the Laysan Rail's extinction?

A. The vegetation on the Laysan Rail's home island was decimated when rabbits were introduced to the island in the 1910s.

B. When attempts were made to relocate the Laysan Rail to other islands, the birds lost the geographical cues that they relied on for finding mating sites.

C. The Laysan Rail builds nests under dense ground cover to protect the eggs.

D. An increase in the use of pesticides resulted in a decrease in the numbers of flies and moths present in the Laysan Rails territory.

E. Many species nested.in the same types of vegetation as the Laysan Rail.

How can we assume here that Laysan Rails eat flies and moths?
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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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11 Jan 2019, 10:44
goobo wrote:
Bunuel wrote:
The Laysan Rail, an insectivore bird once present on several of the Hawaiian Islands, can no longer be found and is thought to be extinct. Scientists originally thought that a decrease in the amount of ground vegetation available for nesting was responsible for the decline of the bird. However, they now believe that increased competition for food was ultimately responsible for the Laysan Rail's inability to survive.

Which of the following would best help to account for the change in the accepted explanation for the Laysan Rail's extinction?

A. The vegetation on the Laysan Rail's home island was decimated when rabbits were introduced to the island in the 1910s.

B. When attempts were made to relocate the Laysan Rail to other islands, the birds lost the geographical cues that they relied on for finding mating sites.

C. The Laysan Rail builds nests under dense ground cover to protect the eggs.

D. An increase in the use of pesticides resulted in a decrease in the numbers of flies and moths present in the Laysan Rails territory.

E. Many species nested.in the same types of vegetation as the Laysan Rail.

How can we assume here that Laysan Rails eat flies and moths?

In the passage in start it is mentioned that the bird is an insectivore......that means it eats insect

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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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11 Jan 2019, 10:57
IMO D

Conclusion: they now believe that increased competition for food was ultimately responsible for the Laysan Rail's inability to survive.

Which of the following would best help to account for the change in the accepted explanation for the Laysan Rail's extinction?

Prethink: Food was the only reason for extinction of Laysan Rail's ...there was some scarcity of food or some competition for food which led to loss of food and hence decline in Laysan Rail

A. The vegetation on the Laysan Rail's home island was decimated when rabbits were introduced to the island in the 1910s.---Wrong, It does not mention any detail pertinent to food source of laysan being affected by rabbit

B. When attempts were made to relocate the Laysan Rail to other islands, the birds lost the geographical cues that they relied on for finding mating sites.----irrelevant

C. The Laysan Rail builds nests under dense ground cover to protect the eggs.----Wrong, does not address the conclusion

D. An increase in the use of pesticides resulted in a decrease in the numbers of flies and moths present in the Laysan Rails territory.--Correct, matches with prethinking

E. Many species nested.in the same types of vegetation as the Laysan Rail.---Wrong, because even if other species nested on same type of vegetation, it does not provides the result of that nesting....There could have been no effect or some effect or Most effect
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Re: The Laysan Rail, an insectivore bird once present on several of the Ha  [#permalink]

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15 Jan 2019, 05:15
Bunuel wrote:
The Laysan Rail, an insectivore bird once present on several of the Hawaiian Islands, can no longer be found and is thought to be extinct. Scientists originally thought that a decrease in the amount of ground vegetation available for nesting was responsible for the decline of the bird. However, they now believe that increased competition for food was ultimately responsible for the Laysan Rail's inability to survive.

Which of the following would best help to account for the change in the accepted explanation for the Laysan Rail's extinction?

A. The vegetation on the Laysan Rail's home island was decimated when rabbits were introduced to the island in the 1910s.

B. When attempts were made to relocate the Laysan Rail to other islands, the birds lost the geographical cues that they relied on for finding mating sites.

C. The Laysan Rail builds nests under dense ground cover to protect the eggs.

D. An increase in the use of pesticides resulted in a decrease in the numbers of flies and moths present in the Laysan Rails territory.

E. Many species nested.in the same types of vegetation as the Laysan Rail.

KAPLAN OFFICIAL EXPLANATION:

D

Scientists first attributed the bird's extinction to a loss of ground vegetation, which the birds used for nesting, but they now believe that a lack of food (insects) was actually responsible. Let's examine the choices to find one that explains why scientists changed their opinion.

(A) provides evidence that a decrease in vegetation did in fact occur. If anything, that would have strengthened the hypothesis that loss of vegetation led to the birds' extinction, rather than causing the scientists to find a new explanation. (B) is out of scope. The passage doesn't concern relocation to other islands, and neither extinction hypothesis has anything to do with mating habits. (C) would strengthen the vegetation hypothesis, by providing evidence of how important the vegetation was to the birds' survival. (E) focuses on other species. Moreover, it supports the vegetation theory, not the food theory. (D) might explain the shift. Since the birds eat insects (Sentence 1), a decrease in the insect population would increase competition for food and could lead to extinction if the birds were not able to compete effectively.
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Re: The Laysan Rail, an insectivore bird once present on several of the Ha   [#permalink] 15 Jan 2019, 05:15
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# The Laysan Rail, an insectivore bird once present on several of the Ha

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