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In the Sonoran Desert of northwestern Mexico and southern Arizona, t

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Re: In the Sonoran Desert of northwestern Mexico and southern Arizona, t  [#permalink]

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New post 13 Dec 2018, 14:01
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T1101 wrote:
Dear Verbal Expert,

even after reading the discussion I am still not able to fully understand Question 2... I understand why B is correct, but I do not understand why C is incorrect. Is it because of the "not a preferred food"? The passage never talks about explicitly about preference.

Thank you in advance!!!

(Book Question: 440)
According to the passage, which of the following types of nectar-feeding pollinators is likely to be an unreliable pollinator of a particular cactus flower?
A. A dietary specialist whose abundance is typically high in relation to that of the flower
B. A dietary specialist whose abundance is at times significantly lower than that of the flower
C. A dietary generalist for whom that flower???s nectar is not a preferred food but is the most consistently available food
D. A dietary generalist for whom that flower???s nectar is slightly preferred to other available foods
E. A dietary generalist that evolved from a species of dietary specialists

The passage does mention preference explicitly in lines 22-24:

    Or, they can be dietary specialists, but their abundance may vary widely from year to year, resulting in variable pollination of their preferred food species.

However, the role of preference is implied throughout the passage.

  • The distinction between "generalist" and "specialist" begins with the premise that animals pollinate food species (in other words, animals pollinate what they feed on).
  • Some pollinators (the generalists) pollinate whatever food species are available, while other pollinators (the specialists) do have a special preference, which can only be satisfied by a narrow range of food species.

So how we do we eliminate choice (C)? Well, here's the author says when describing reasons what could make a pollinator unreliable:

    Pollinators can be unreliable for several reasons. They can be dietary generalists whose fidelity to a particular species depends on the availability of alternative food sources.

According to the passage, a dietary generalist will be faithful to a particular food species if it's available. They don't have special food preferences. If they're feeding on a certain type of nectar, but an alternative food sources become available, then the generalists will begin pollinating that alternative food source instead. Is that what choice (C) says?

Quote:
C. A dietary generalist for whom that flower's nectar is not a preferred food but is the most consistently available food
(is likely to be an unreliable pollinator of that flower).

Nope. (C) tells us that this flower is the most consistently available food for that generalist. If that's true, then we'd expect the generalist to be a reliable pollinator for this flower, because the generalist pollinates whatever is available.

But choice (C), as it's written, states that the generalist is likely to be an unreliable pollinator for this flower.

This contradicts the expected behavior of generalists -- so we must eliminate it.

I hope this helps!
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Re: In the Sonoran Desert of northwestern Mexico and southern Arizona, t  [#permalink]

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New post 09 Jun 2019, 21:12
GMATNinja wrote:
T1101 wrote:
Dear Verbal Expert,

even after reading the discussion I am still not able to fully understand Question 2... I understand why B is correct, but I do not understand why C is incorrect. Is it because of the "not a preferred food"? The passage never talks about explicitly about preference.

Thank you in advance!!!

(Book Question: 440)
According to the passage, which of the following types of nectar-feeding pollinators is likely to be an unreliable pollinator of a particular cactus flower?
A. A dietary specialist whose abundance is typically high in relation to that of the flower
B. A dietary specialist whose abundance is at times significantly lower than that of the flower
C. A dietary generalist for whom that flower???s nectar is not a preferred food but is the most consistently available food
D. A dietary generalist for whom that flower???s nectar is slightly preferred to other available foods
E. A dietary generalist that evolved from a species of dietary specialists

The passage does mention preference explicitly in lines 22-24:

    Or, they can be dietary specialists, but their abundance may vary widely from year to year, resulting in variable pollination of their preferred food species.

However, the role of preference is implied throughout the passage.

  • The distinction between "generalist" and "specialist" begins with the premise that animals pollinate food species (in other words, animals pollinate what they feed on).
  • Some pollinators (the generalists) pollinate whatever food species are available, while other pollinators (the specialists) do have a special preference, which can only be satisfied by a narrow range of food species.

So how we do we eliminate choice (C)? Well, here's the author says when describing reasons what could make a pollinator unreliable:

    Pollinators can be unreliable for several reasons. They can be dietary generalists whose fidelity to a particular species depends on the availability of alternative food sources.

According to the passage, a dietary generalist will be faithful to a particular food species if it's available. They don't have special food preferences. If they're feeding on a certain type of nectar, but an alternative food sources become available, then the generalists will begin pollinating that alternative food source instead. Is that what choice (C) says?

Quote:
C. A dietary generalist for whom that flower's nectar is not a preferred food but is the most consistently available food
(is likely to be an unreliable pollinator of that flower).

Nope. (C) tells us that this flower is the most consistently available food for that generalist. If that's true, then we'd expect the generalist to be a reliable pollinator for this flower, because the generalist pollinates whatever is available.

But choice (C), as it's written, states that the generalist is likely to be an unreliable pollinator for this flower.

This contradicts the expected behavior of generalists -- so we must eliminate it.

I hope this helps!


Thanks for sharing this. A few things. Wouldn't the term "generalist", which suggests that they can pollinate more than one flower, indicate that a generalist would pollinate according to preference, and not abundance? It would make more sense for a specialist to prioritize abundance, since they can only feed on a select few flowers, whereas a generalist has more choices and can therefore be more picky. This would make Answer C more correct.

In addition, Answer A specifically mentions "at times significantly lower", whereas the excerpt in the passage quotes "their abundance may be CHRONICALLY low relative to the availability of flowers". It seems to be the passage is suggesting the only chronically low abundance would be a reliability issue, but if it happens once in a while ("at times"), the effects are not significant enough to warrant the "unreliable" label.

Let me know if the above makes sense. Based on the logic above, I am still struggling to understand why B is correct and not C. Thank you!
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Re: In the Sonoran Desert of northwestern Mexico and southern Arizona, t  [#permalink]

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New post 12 Jun 2019, 07:01
felixduan320 wrote:
Thanks for sharing this. A few things. Wouldn't the term "generalist", which suggests that they can pollinate more than one flower, indicate that a generalist would pollinate according to preference, and not abundance? It would make more sense for a specialist to prioritize abundance, since they can only feed on a select few flowers, whereas a generalist has more choices and can therefore be more picky. This would make Answer C more correct.

In addition, Answer A specifically mentions "at times significantly lower", whereas the excerpt in the passage quotes "their abundance may be CHRONICALLY low relative to the availability of flowers". It seems to be the passage is suggesting the only chronically low abundance would be a reliability issue, but if it happens once in a while ("at times"), the effects are not significant enough to warrant the "unreliable" label.

Let me know if the above makes sense. Based on the logic above, I am still struggling to understand why B is correct and not C. Thank you!

The passage tells us that a generalist can be an unreliable pollinator because its "fidelity to a particular species depends on the availability of alternative food sources."

This tells us that a generalist doesn't really have a preference for which plant it eats -- it just eats whatever is most readily available. Let's say that out of plants X, Y, and Z, only plant X is available. Generalists will just eat plant X and be happy to do so! Now say that plants Y and Z move into the area -- the generalist doesn't remain faithful to plant X, but eats whatever is most convenient. Plant X will not get as much attention from the generalist -- so from plant X's perspective, the generalist is an unreliable pollinator when other plants are available for it to feed on.

The main point is that the generalist doesn't choose what it eats based on preference -- it chooses based on availability.

Take another look at (C):
Quote:
C. A dietary generalist for whom that flower’s nectar is not a preferred food but is the most consistently available food [is an unreliable pollinator].

Based on the discussion above, we know that generalists decide what to eat based on availability. So, it will reliably eat (and therefore pollinate) "the most consistently available food." This is essentially the opposite of answer choice (C), so (C) is incorrect.

To understand why (B) is correct, take a look at the two reasons identified in the passage to explain why a specialist may be an unreliable pollinator:
  • "their abundance may vary widely from year to year, resulting in variable pollination of their preferred food species." OR
  • " their abundance may be chronically low relative to the availability of flowers."

Now take a look at answer choice (B):
Quote:
B. A dietary specialist whose abundance is at times significantly lower than that of the flower

You are correct to point out that (B) doesn't align well with a case in which the specialist population is "chronically low." However, this answer choice does fit nicely with the other case, in which the specialists' "abundance may vary widely." Because (B) specifically tells us that the specialist's abundance is "at times significantly lower than that of the flower," we can say that it is not consistently available to pollinate all of the flowers. Therefore, this particular specialist is an unreliable pollinator, and (B) is correct.

I hope that helps!
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Re: In the Sonoran Desert of northwestern Mexico and southern Arizona, t  [#permalink]

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New post 19 Jun 2019, 00:55
OG 2018-- using POE to pick Rt answer


439) The primary purpose of the passage is to

A. compare the adaptive responses of several species of columnar cacti in the Sonoran Desert with those in the arid tropical regions of southern Mexico
choice A -Eliminate because Main Purpose of Passage is not to compare adaptive responses. It just talks about adaptive response of Sonaran Dessert Cacti's evolution and its reason.[/b][/b]
B. discuss some of the possible causes of the relatively low abundance of migratory nectar-feeding bats in the Sonoran Desert
Choice B- Low Abundance of Bat is discussed but not its causes. So eliminate.
C. provide a possible explanation for a particular evolutionary change in certain species of columnar cacti in the Sonoran Desert
Choice C- Correct . It clearly explains main purpose of the passage. First talks about Evolution of the Columnar Cacti, Second para discusses reasons for evolution
D. present recent findings that challenge a particular theory as to why several species of columnar cacti in the Sonoran Desert have expanded their range of pollinators
Choice D- Eliminate as theory of evolutionary changes are discussed of columnar cacti but not CHALLENGED.
E. compare the effectiveness of nocturnal and diurnal pollination for several different species of columnar cacti in the Sonoran Desert
Choice E - Eliminate as Effectiveness of Nocturnal and diurnal pollination not discussed . Mix up trap where words from Passage are used to create trap answer choice.


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Re: In the Sonoran Desert of northwestern Mexico and southern Arizona, t  [#permalink]

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New post 19 Jun 2019, 01:10
Question: 440
According to the passage, which of the following types of nectar-feeding pollinators is likely to be an unreliable pollinator of a particular cactus flower?
A. A dietary specialist whose abundance is typically high in relation to that of the flower
Choice A- Says opposite to what is mentioned in second para of the passage.-", they can be dietary specialists, but their abundance may vary widely from year to year" So it does not say high abundance but says abundance vary.
B. A dietary specialist whose abundance is at times significantly lower than that of the flower
Correct Choice B-Refer para II Line 25[/b][color=#00a651]
C.A dietary generalist for whom that flower’s nectar is not a preferred food but is the most consistently available food[color=#111111]
Choice C - Mix up word trap- uses words from passage but conveys different meaning than what is said in passage. ( Ref line 24) Here if we go by meaning it should be reliable pollinator since flower nectar is most consistently available food .Eliminate C
D. A dietary generalist for whom that flower’s nectar is slightly preferred to other available foods
Answer Choice D-If Flower nectar is preferred - it will be reliable pollinator. Question talks about unreliable pollinator.- Eliminate D
E. A dietary generalist that evolved from a species of dietary specialists
Choice E -Passage does not discuss about this, so Eliminate.

For detail question we need to find match from the passage.


Question: 441
According to the passage, present-day columnar cacti in the Sonoran Desert differ from their close relatives in southern Mexico in that the Sonoran cacti
A. have flowers that remain open after sunset
Choice A- Uses one word off trap- where just one word is incorrect and changes the meaning from what is given in the passage. Passage says that Line 11"Sonoran Desert cacti have evolved to remain open after sunrise" Here it says Sunset. Hence Eliminate
B. are pollinated primarily by dietary specialists
Ans Choice B-Both are pollinated by dietary specialist- nectar feeding bats. So that is not the difference but common factor. So Eliminate. Dont forget we are looking for difference.
C. can be pollinated by nectar-feeding bats
Again same as ans Choice B- So Eliminate as it is common factor between both Sonaran Dessert Cacti and their close relatives in southern Mexico.
D. have stigmas that are unreceptive to pollination at night
Both are pollinated at night time though Sonaran Dessert cacti have evolved to getting pollinated day time also, but basically both get pollinated at night so there stigmas are receptive. This answer choice Note convery reverse of what is given in the passage. Hence Eliminate
E. are sometimes pollinated by diurnal pollinators
Correct- Passage talks about how Sonaran Dessert cacti have evolve to get pollinated by diurnal pollinators. unlike its close relative in southern mexico.

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Re: In the Sonoran Desert of northwestern Mexico and southern Arizona, t  [#permalink]

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New post 12 Aug 2019, 22:44
Hi, LeoGT
I had a query similar to yours for Q.2
Note that the passage describes in general about the cases when pollinators can be unreliable. However, the question mentions 'particular cactus flower', the answer for which is "during spring in the Sonoran Desert, the nectar-feeding bats are specialists feeding on carbon, saguaro, and organ-pipe flowers. However, whereas cactus-flower abundance tends to be high during spring, bat population densities tend to be low except near maternity roosts. Moreover, in spring, diurnal cactus-pollinating birds are significantly more abundant inthis region than are the nocturnal bats. Thus, with bats
being unreliable cactus-flower pollinators".

Hope this helps.
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Re: In the Sonoran Desert of northwestern Mexico and southern Arizona, t   [#permalink] 12 Aug 2019, 22:44

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