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# Of the many organisms found in marine ecosystems, sea otters play a un

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Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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Updated on: 11 Oct 2019, 23:38
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New Project RC Butler 2019 - Practice 2 RC Passages Everyday
Passage # 215, Date : 19-Jul-2019
This post is a part of New Project RC Butler 2019. Click here for Details

Of the many organisms found in marine ecosystems, sea otters play a uniquely significant role in maintaining their environments. Sea otters (Enhydra lutris) are a keystone species, a species whose effect on their environment is disproportionately great relative to their size in numbers or weight. Keystone species keep the growth of populations of other species in check and are thereby a determining factor of the type and number of other species in a community; keystone species are so named because their role is analogous to that of a keystone in an arch: while keystones bear the least amount of pressure among the components of an arch, the arch collapses without them.

The sea otter's reputation as a keystone species is largely a consequence of its affinity for sea urchins. Sea otters are known to prey upon over 100 different species, but the bulk of their diet consists of sea urchins and other marine invertebrates. Sea urchins are such highly preferred prey that sea otters have been known to significantly deplete urchin populations. In marine ecosystems at equilibrium, however, sea otters are often the primary force that keeps populations of sea urchins in check. Without sea otters, sea urchins and other seafloor herbivores would graze on help holdfasts, causing kelp to drift away from their substrates and die. The aggregate result of many such events leads to the destruction of entire kelp beds, resulting in a loss of habitat and nutrients for other organisms in the ecosystem. The extended consequences include local extinction of other species and vast urchin barrens: subtidal areas where the unchecked population growth of sea urchins has caused a dearth of kelp and, therefore, other marine species.

This ecological cascade effect of secondary extinctions resulting from a decrease in otter populations and corresponding growth in urchin populations was observed throughout the 19th century along the Pacific coast of North America. Sea otters had been aggressively hunted for their rich pelts since before the 1600s, and this practice was not outlawed until an international treaty was signed in 1911 to prevent further exploitation. Prior to the enforcement of the treaty, hunters caused sea otter populations to decline; this in turn caused sea urchin populations to explode. Consequently, the urchin populations overexploited their primary food source, kelp, creating a preponderance of urchin barrens.

1. The author's tone towards sea otters could best be described as

(A) disdainful
(B) dispassionate
(C) concerned
(D) critical
(E) jovial

Spoiler: :: OE
The primary purpose of this passage is to highlight the significance of the sea otter in its environment, and the first paragraph spends multiple sentences noting the meaning of keystone species to give a phrase to this importance.

The Sea Otter as a Keystone Species is an apt summary of the passage, and thus E is the correct answer.

Answer choice A is incorrect, as the prominence of the sea urchin in this passage is mitigated by the impact that the otter also has on kelp beds and other features of the ecosystem.

Answer choice D is similarly incorrect, as the urchins are one facet of the otter's importance; D fails to mention the otter at all.

Choices B and C are each too broad in scope, as this passage deals specifically with the sea otter; those answer choices seek to describe entire ecological topics in much too broad a scope.

2. Which of the following would be the most likely title for this passage?

(A) The Sea Otter and the Sea Urchin
(B) Ecological Cascade Effects in Global Ecosystems
(C) Marine Holdfasts: The Key to Biodiversity
(D) A Study of Urchin Barrens
(E) The Sea Otter as a Keystone Species

Spoiler: :: OE

The first paragraph of the passage introduces sea otters and describes their role as a keystone species; the second details the effect that sea otters have in two types of populations, and the third demonstrates the effect that the otters have had on human society.

Thus, the passage as a whole is written to explain the significance of sea otters, which is the point of answer choice D.

While choices B, C, and E are each touched upon in the passage, each is done to support the overall significance of sea otters, and none is the primary focus of the passage.

Answer choice A is farther out of scope; the passage is descriptive in nature, making the verb advocate incorrect, and the passage only describes the effect of otters on the sea urchins, but does not talk about any type of strategy for doing so.

3. The primary purpose of this passage is to

(A) advocate a strategy for keeping sea urchins in check.
(B) explain the absence of kelp in the North American Pacific coast.
(C) outline the dietary habits of sea otters.
(D) describe the significance of sea otters in their ecosystems.
(E) define the term "keystone species."

Spoiler: :: OE

The term holdfast is used in the second paragraph: Without sea otters, sea urchins and other seafloor herbivores would graze on kelp holdfasts, causing kelp to drift away from their substrates and die.

The effect of sea urchins and other herbivores on these holdfasts would be to permit kelp to drift away; thus, it can be inferred that without interference from herbivores, the role of the holdfast is to anchor the kelp, and B is the correct answer.

Answer choice A is incorrect as the kelps is the organism, not the holdfast itself.

Choices C, D, and E are unsupported by the passage.

4. Based on the information in the passage, what is the most likely meaning of holdfast?

(A) organisms that dwell at the lowest level of a body of water
(B) a root-like structure that anchors an organism
(C) aquatic arthropods that live in marine environments
(D) rocks used by sea otters to dislodge prey and open shells
(E) the act of embracing feverishly

5. According to the passage, which of the following could be most reasonably inferred about kelp?

(A) Kelp forests provide a unique habitat for a variety of marine organisms.
(B) Kelp is an important food source for coastal Californians.
(C) Kelp forests occur worldwide throughout temperate and polar coastal oceans.
(D) Kelp is an important part of the sea otter's diet.
(E) A 1911 treaty reinvigorated kelp forests by requiring otter hunters to plant marine algae.
Spoiler: :: OE

The final sentence of the second paragraph states that: The extended consequences include local extinction of other species and vast urchin barrens: subtidal areas where the unchecked population growth of sea urchins has caused a dearth of kelp and, therefore, other marine species.

This sentence sets the cause and effect relationship that the lack of kelp led to the lack of other marine species.

Thus, it can be inferred that kelp provide a unique habitat for such species that were unable to survive in the absence of kelp.

Originally posted by solitaryreaper on 25 Sep 2014, 09:17.
Last edited by SajjadAhmad on 11 Oct 2019, 23:38, edited 5 times in total.
Updated - Complete topic (954).
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Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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03 Dec 2019, 19:23
1
QTN 5
Official explanation

The final sentence of the second paragraph states that: The extended consequences include local extinction of other species and vast urchin barrens: subtidal areas where the unchecked population growth of sea urchins has caused a dearth of kelp and, therefore, other marine species. This sentence sets the cause and effect relationship that the lack of kelp led to the lack of other marine species. Thus, it can be inferred that kelp provide a unique habitat for such species that were unable to survive in the absence of kelp.

Q4

The term holdfast is used in the second paragraph: Without sea otters, sea urchins and other seafloor herbivores would graze on kelp holdfasts, causing kelp to drift away from their substrates and die. The effect of sea urchins and other herbivores on these holdfasts would be to permit kelp to drift away; thus, it can be inferred that without interference from herbivores, the role of the holdfast is to anchor the kelp, and B is the correct answer. Answer choice A is incorrect as the kelps is the organism, not the holdfast itself. Choices C, D, and E are unsupported by the passage.

Q2

The primary purpose of this passage is to highlight the significance of the sea otter in its environment, and the first paragraph spends multiple sentences noting the meaning of keystone species to give a phrase to this importance. The Sea Otter as a Keystone Species is an apt summary of the passage, and thus E is the correct answer. Answer choice A is incorrect, as the prominence of the sea urchin in this passage is mitigated by the impact that the otter also has on kelp beds and other features of the ecosystem. Answer choice D is similarly incorrect, as the urchins are one facet of the otter's importance; D fails to mention the otter at all. Choices B and C are each too broad in scope, as this passage deals specifically with the sea otter; those answer choices seek to describe entire ecological topics in much too broad a scope.
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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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07 May 2018, 05:42

VERITAS PREP OFFICIAL SOLUTION:

The final sentence of the second paragraph states that: The extended consequences include local extinction of other species and vast urchin barrens: subtidal areas where the unchecked population growth of sea urchins has caused a dearth of kelp and, therefore, other marine species. This sentence sets the cause and effect relationship that the lack of kelp led to the lack of other marine species. Thus, it can be inferred that kelp provide a unique habitat for such species that were unable to survive in the absence of kelp.
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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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30 Aug 2018, 07:40
Quote:
1. The author's tone towards sea otters could best be described as

(A) disdainful
(B) dispassionate
(C) concerned
(D) critical
(E) jovial

How the answer is B.
Overall the passage author doesn't seem to be dispassionate towards sea otters.\

Thanks!
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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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19 Jul 2019, 12:31
How to find the answer to question 4?
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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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21 Jul 2019, 22:26
In the 2nd paragraph read lines 20-22

Without sea otters, sea urchins and other seafloor herbivores would graze on kelp holdfasts, causing kelp to drift away from their substrates and die.

Options A, C, D and E did'nt supported by these lines only Option B is supported

Moubani wrote:
How to find the answer to question 4?

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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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21 Jul 2019, 23:31
Q1 gmat1393

Quote:
Of the many organisms found in marine ecosystems, sea otters play a uniquely significant role in maintaining their environments. Sea otters (Enhydra lutris) are a keystone species, a species whose effect on their environment is disproportionately great relative to their size in numbers or weight. Keystone species keep the growth of populations of other species in check and are thereby a determining factor of the type and number of other species in a community; keystone species are so named because their role is analogous to that of a keystone in an arch: while keystones bear the least amount of pressure among the components of an arch, the arch collapses without them.

-

in the first para author tells us that "otters = keystone species" ...author is neither + or - about this !!!

it is intimidating to think that author has a POV by the words " uniquely significant" ...but please note that the author is just describing the necessay object here.. by stating that " oxygen is necessary for humans" i am not taking a stand for oxygen... i am just being descriptive !!! here author is also being descriptive..
Quote:
The sea otter's reputation as a keystone species is largely a consequence of its affinity for sea urchins. Sea otters are known to prey upon over 100 different species, but the bulk of their diet consists of sea urchins and other marine invertebrates. Sea urchins are such highly preferred prey that sea otters have been known to significantly deplete urchin populations. In marine ecosystems at equilibrium, however, sea otters are often the primary force that keeps populations of sea urchins in check. Without sea otters, sea urchins and other seafloor herbivores would graze on help holdfasts, causing kelp to drift away from their substrates and die. The aggregate result of many such events leads to the destruction of entire kelp beds, resulting in a loss of habitat and nutrients for other organisms in the ecosystem. The extended consequences include local extinction of other species and vast urchin barrens: subtidal areas where the unchecked population growth of sea urchins has caused a dearth of kelp and, therefore, other marine species.

- here the author tells us : WHY SEA OTTERS ARE KEYSTONE
- no + or - POV by author

Quote:
This ecological cascade effect of secondary extinctions resulting from a decrease in otter populations and corresponding growth in urchin populations was observed throughout the 19th century along the Pacific coast of North America. Sea otters had been aggressively hunted for their rich pelts since before the 1600s, and this practice was not outlawed until an international treaty was signed in 1911 to prevent further exploitation. Prior to the enforcement of the treaty, hunters caused sea otter populations to decline; this in turn caused sea urchin populations to explode. Consequently, the urchin populations overexploited their primary food source, kelp, creating a preponderance of urchin barrens.

- function : how NO OTTER would indirectly affect something else...followed by examples
- again the author ony tells us what happened IN HISTORY when otter was depleted ... is he saying they should be saved NOW???
is he concerned that they are depleting?? NOOO
All the author is expanding on the fact that "OTTER IS A KEYSONE SPECIEIS " .....

1. The author's tone towards sea otters could best be described as

(A) disdainful - no negarivity - WRONG
(B) dispassionate - plainly explanding on a topic "otters are keysrone species " ...pure description.. NO STANDS
(C) concerned- plainly descriptive
(D) critical- WRONG
(E) jovial - NO POSITIVITY - WRONG
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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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31 Jul 2019, 17:46
I am still not convinced with option B for question 1.
Sea otter, a keystone organism, maintains the ecology system indirectly. Though their the size and number might be less, sea otters play a key role to sustain the other organisms, keeping the urchins in check.
Prior to 1911, excessive hunting had caused depletion of sea otters, eventually leading to exploitation of other organisms by urchins.

With the above understanding, I think the author is concerned about sea otters.
C should be the correct choice.
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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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04 Nov 2019, 11:53
Can anyone please explain the answer of question 2 and question 4.
Thanks!
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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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06 Nov 2019, 05:27
priyaarorastep wrote:
Can anyone please explain the answer of question 2 and question 4.
Thanks!

https://gmatclub.com/forum/of-the-many- ... l#p2320112

Thanks
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Re: Of the many organisms found in marine ecosystems, sea otters play a un  [#permalink]

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06 Dec 2019, 04:04
Moubani wrote:
How to find the answer to question 4?

It gets mentioned in the latter lines where the paragraph mentions "this leads to a loss of habitat", this gives us a clue that kelp holdfasts act as a place to reside for some species and that idea is reciprocated in option saying that it anchors...
I hope you understand.
Re: Of the many organisms found in marine ecosystems, sea otters play a un   [#permalink] 06 Dec 2019, 04:04
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