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While the most abundant and dominant species within a particular ecosy

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Re: While the most abundant and dominant species within a particular ecosy  [#permalink]

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New post 18 Sep 2018, 07:43
Dear All ; For Q2, I need your help in understanding why B&E may not be best answers. Though I chose the correct answer, I had a lot to convince myself for the right choice. What' the key point in B&E that helps eliminate it with the POE process ?

2. Which of the following hypothetical experiments most clearly exemplifies the method of identifying species, roles that the author considers problematic?

B. A species of fish that is a keystone species in one marine ecosystem is introduced into another marine ecosystem to see whether the species will come to occupy a keystone role. .. this explains wrt. Community diversity where the fish, if removed from one marine ecosystem will impact that ecosystem and KS status( if it was or some other species was KS because of fish, elimination of fish will impact the ecosystem. Same manner it will have it' effect on new ecosystem). I had eliminated this option because no reference of fish being KS was mentioned and hence, out of context. Is there anything else ?

E. In a grassland experiencing a changing climate, patterns of species extinction are traced in order to evaluate the effect of climate changes on keystone species in that grassland. - Though [i]I understand author/passage has only mentioned the community diversity and length of association as key and hence stuck of this option. Is there anything else to eliminate besides rationale shared ?[/i]
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New post 18 Sep 2018, 07:46
Dear All ; For Q2, I need your help in understanding why B&E may not be best answers. Though I chose the correct answer, I had a lot to convince myself for the right choice. What' the key point in B&E that helps eliminate it with the POE process ?

2. Which of the following hypothetical experiments most clearly exemplifies the method of identifying species, roles that the author considers problematic?

B. A species of fish that is a keystone species in one marine ecosystem is introduced into another marine ecosystem to see whether the species will come to occupy a keystone role. .. this explains wrt. Community diversity where the fish, if removed from one marine ecosystem will impact that ecosystem and KS status( if it was or some other species was KS because of fish, elimination of fish will impact the ecosystem. Same manner it will have it' effect on new ecosystem). I had eliminated this option because no reference of fish being KS was mentioned and hence, out of context. Is there anything else ?

E. In a grassland experiencing a changing climate, patterns of species extinction are traced in order to evaluate the effect of climate changes on keystone species in that grassland. - Though I understand author/passage has only mentioned the community diversity and length of association as key and hence stuck of this option. Is there anything else to eliminate besides rationale shared ?
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Re: While the most abundant and dominant species within a particular ecosy  [#permalink]

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New post 03 Oct 2018, 14:33
1

Question 2


proabhinav wrote:
Dear All ; For Q2, I need your help in understanding why B&E may not be best answers. Though I chose the correct answer, I had a lot to convince myself for the right choice. What' the key point in B&E that helps eliminate it with the POE process ?

2. Which of the following hypothetical experiments most clearly exemplifies the method of identifying species' roles that the author considers problematic?

We can eliminate choices most confidently when we are clear on what the question is asking us to do. This enables us to get rid of choices that simply aren't answering the question.

In this case, Question #2 presents five hypothetical experiments. The question stem asks us which of the experiments most clearly exemplifies the method of identifying species' roles that the author considers problematic.

According to the author's own words, what method does the author consider to be problematic?

    "But because complex species interactions may be involved, identifying a keystone species by removing the species and observing changes in the ecosystem is problematic."

The method in question is "removing the species and observing changes in the ecosystem." So we're going to eliminate any choice that doesn't name this method of identifying the role of a given species.

Quote:
(B) A species of fish that is a keystone species in one marine ecosystem is introduced into another marine ecosystem to see whether the species will come to occupy a keystone role.

The method used in experiment (B) is introducing a species into an ecosystem. This is not the same as removing a species from its ecosystem. That's why we eliminate (B).

Quote:
(E) In a grassland experiencing a changing climate, patterns of species extinction are traced in order to evaluate the effect of climate changes on keystone species in that grassland.

The method used in experiment (E) is tracing patterns of species extinction. This has nothing to do with removing a species from its ecosystem. That's why we eliminate (E).


Question 3


csaluja wrote:
Could someone please explain the reasoning behind option B for Q3? I choose C instead based on this sentence from the passage: "Keystone status appears to depend on context, whether of particular geography or of such factors as community diversity (for example, a reduction in species diversity may thrust more of the remaining species into keystone roles). Isn't the bold part what option C is saying?

That's not quite what choice (C) says. Here's (C) again:
Quote:
(C) Close observation of a savannah ecosystem reveals that more species occupy keystone roles within that ecosystem than biologists had previously believed.

There's no mention here of a reduction in species diversity, and definitely no mention of remaining species being thrust into keystone roles.

Instead, (C) describes a scenario where there is no change to the species, no change to the roles that species play, and no change to the species' setting. The only thing at work here is biologists' belief in the roles that species occupy (which change after close observation).

This doesn't line up with the passage's description of keystone status depending on context. Instead, it focuses on biologist's observation of keystone status. That's why we eliminate (C).

Compare this to choice (B):
Quote:
(B) A species of iguana occupies a keystone role on certain tropical islands, but does not play that role on adjacent tropical islands that are inhabited by a greater number of animal species.

(B) remains the best answer choice because it does spell out an example of a keystone role depending on context. The iguana's keystone role on one island doesn't exist when the iguana inhabits a different island.

I hope this helps!
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Re: While the most abundant and dominant species within a particular ecosy  [#permalink]

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New post 16 Oct 2018, 06:48
main point - keystone species; example ; determining keystone.

1. The passage mentions which of the following as a factor that affects the role of P. ochraceus as a keystone species within different habitats?

Moreover, whereas P. ochraceus occupies an unambiguous keystone role on wave-exposed rocky headlands, in more wave-sheltered habitats the impact of P. ochraceus predation is weak or nonexistent, and at certain sites sand burial is responsible for eliminating mussels.

(A) The degree to which the habitat is sheltered from waves -

-----------------------------------

2. Which of the following hypothetical experiments most clearly exemplifies the method of identifying species, roles that the author considers problematic?

(C) In order to determine whether a species of monkey is a keystone species within a particular ecosystem, the monkeys are removed from that ecosystem and the ecosystem is then studied.

-----------------------------------------

3. Which of the following, if true, would most clearly support the argument about keystone status advanced in the last sentence of the passage?

Keystone status appears to depend on context, whether of particular geography or of such factors as community diversity (for example, a reduction in species diversity may thrust more of the remaining species into keystone roles) and length of species interaction (since newly arrived species in particular may dramatically affect ecosystems).

The one follows these two rules.

(B) A species of iguana occupies a keystone role on certain tropical islands, but does not play that role on adjacent tropical islands that are inhabited by a greater number of animal species.
-------------------------------------------------

4. The passage suggests which of the following about the identification of a species as a keystone species?

(A) Such an identification depends primarily on the species’ relationship to the dominant species. - this is not sure in all such cases.
(B) Such an identification can best be made by removing the species from a particular ecosystem and observing changes that occur in the ecosystem. - will it follows every such case, for sure no.
(C) Such an identification is likely to be less reliable as an ecosystem becomes less diverse. - this way one can not identify.
(D) Such an identification seems to depend on various factors within the ecosystem. - yes , two are defined in last sentence.
(E) Such an identification can best be made by observing predation behavior. - no
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Re: While the most abundant and dominant species within a particular ecosy  [#permalink]

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New post 31 Oct 2018, 01:52
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What is the level of this passage?
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Re: While the most abundant and dominant species within a particular ecosy  [#permalink]

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New post 15 Nov 2018, 13:58
Anyone else found the passage intimating? Surprised this is only 600-700 difficulty :O
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Re: While the most abundant and dominant species within a particular ecosy &nbs [#permalink] 15 Nov 2018, 13:58

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