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Target Test Prep Representative
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GRE 1: Q170 V170
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Re: As Gilbert White, Darwin, and others observed long ago, all [#permalink]
Expert Reply
mind wrote:
Carcass. There's a minor typo in the reading passage, but it should be "vital rates" not "vital, rates." Referenced Big Book Test 26 Section 2


Fixed.

thank you sir. I appreciate all the support you students give to this platform. I hope we do even better in the future.

We are working hard to fill in what is missing here.

regards
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Re: As Gilbert White, Darwin, and others observed long ago, all [#permalink]
1
Thank you for answering question 17, RonTargetTestPrep. I found your explanation for why E is wrong is a little difficult to understand. Can you please help explain in an easier way? I actually chose E and eliminated A.

"E. refuting a commonly accepted theory about population density and offering a new alternative"

For me, 'the commonly accepted theory' here is the school of thought mentioned in the passage: 'the dichotomy of density-dependent and density-independent'. I think what the author did at the end of the passage was to refute the dichotomy: "But it now seems clear that all populations are regulated by a mixture of density-dependent and density-independent effects in varying proportions." This means 'refuting' wording is correct

Isn't it true that the author offers a new alternative: "all populations are regulated by a mixture of density-dependent and density-independent" not just the one or another just like dichotomy suggested

What am I doing wrong here?

I eliminated A bc it uses the phrase "two categories of factors." I thought this equals to "the environmental and biological factors," and this phrase is only mentioned at the beginning of the passage. Very brief mentioning, can't be the main or primary thing being discussed in the passage
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Re: As Gilbert White, Darwin, and others observed long ago, all [#permalink]
Anybody help with Q17 - what reason led you to eliminate answer E? A more detailed version of my question is in the previous comment
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Re: As Gilbert White, Darwin, and others observed long ago, all [#permalink]
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------------------------------------------------------------------------------------------


P1

The author starts with presenting a fact: populations grow over the long term. Then the author proceeds by explaining the difficulties related to analyzing the contributing factors to such growth.

Purpose: To portrait the difficulties that scientists can encounter while investigating the variable related to populations' growth.



P2

In this paragraph the author divides populations in 2 groups: the first one depends primarily on density factors while the second one depends on factors unrelated to density.

Purpose: To present 2 kind of populations: density and non density dependent.



P3

Here the author clarifies than no population depends only on non density factors. The density factors could be as small as 1% but they are there (maybe difficult to determine) and from them the long term growth of the population is determined.

Purpose: To point out the presence of density population factors in all the populations and its importance.



P4

In this paragraph the author compares density dependent and non dependent factors respectively to a signal and noise. The signal is easy to determine in populations whose growth is constant or whose oscillations are constant while it is more difficult to isolate the signal from the noise in those populations whose density non dependent factors are significant.

Purpose: to explain density dependent and non dependent factors through the concept of signal and noise and to claim that the two are always present.



Main point

The purpose of this passage is to claim that all populations' growths are characterized by both density dependent and independent factors.



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


1. The author of the passage is primarily concerned with

Pre-thinking

Main point question

The purpose of this passage is to claim that all populations' growths are characterized by both density dependent and independent factors.


(A) discussing two categories of factors that control population growth and assessing their relative importance
In line with pre.thinking

(B) describing how growth rates in natural populations fluctuate over time and explaining why these changes occur
Not in line with prethinking

(C) proposing a hypothesis concerning population sizes and suggesting ways to test it
no hypothesis

(D) posing a fundamental question about environmental factors in population growth and presenting some currently accepted answers
No question mentioned

(E) refuting a commonly accepted theory about population density and offering a new alternative
no commonly accepted theory is refuted



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


2. It can be inferred from the passage that the author considers the dichotomy discussed in the second paragraph to be

Pre-thinking

Inference question

This dichotomy has its uses, but it can cause problems if taken too literally.

Useful but we need to be careful and not to think that they are exclusive


(A) applicable only to erratically fluctuating populations
Cannot be inferred

(B) useful, but only if its limitations are recognized
In line with pre-thinking

(C) dangerously misleading in most circumstances
Cannot be inferred

(D) a complete and sufficient way to account for observed phenomena
Cannot be inferred

(E) conceptually valid, but too confusing to apply on a practical basis
Cannot be inferred


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



3. Which of the following statements can be inferred from the last paragraph?

Pre-thinking

Inference question

Let's evaluate the options


(A) For irregularly fluctuating populations, doubling the number of observations made will probably result in the isolation of density-dependent effects.
Cannot be inferred. Too specific

(B) Density-dependent effects on population dynamics do not occur as frequently as do density-independent effects.
Cannot be inferred

(C) At present, ecologists do not understand any of the underlying causes of the density-dependent effects they observe in population dynamics.
Cannot be inferred

(D) Density-dependent effects on growth parameters are thought to be caused by some sort of biochemical “signaling” that ecologists hope eventually to understand.
Cannot be inferred

(E) It is sometimes possible to infer the existence of a density-dependent factor controlling population growth without understanding its causative mechanism.
For populations that remain relatively constant, or that oscillate around repeated cycles, the signal can be fairly easily characterized and its effects described, even though the causative biological mechanism may remain unknown.



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



4. According to the passage, which of the following is a true statement about density-dependent factors in population growth?

Pre-thinking

Detail question

Let's evaluate the options


(A) They ultimately account for long-term population levels.
From P3: they will usually determine the long-term average population density.

(B) They have little to do with long-term population dynamics.
Opposite

(C) They are always more easily isolated and described than those that are density-independent.
Always sounds too extreme

(D) They include random environmental events.
not mentioned

(E) They contradict current ecological assumptions about population dynamics.
not mentioned




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


5. According to the passage, all of the following behaviors have been exhibited by different populations EXCEPT:

Pre-thinking

Detail question

Let's evaluate the options


(A) roughly constant population levels from year to year
Mentioned in P1

(B) regular cycles of increases and decreases in numbers
Same as for option A

(C) erratic increases in numbers correlated with the weather
Same as for option A

(D) unchecked increases in numbers over many generations
Not mentioned

(E) sudden declines in numbers from time to time
Same as for option A



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


6. The discussion concerning population in lines 24-40 serves primarily to

Pre-thinking

Function question

The purpose is to claim the importance of density dependent factors in assessing the long term growth averages


(A) demonstrate the difficulties ecologists face in studying density-dependent factors limiting population growth
Not in line with pre.thinking

(B) advocate more rigorous study of density-dependent factors in population growth
Not in line with pre.thinking

(C) prove that the death rates of any population are never entirely density-independent
the death rates have little to do here

(D) give an example of how death rates function to limit population densities in typical populations
Not in line with pre.thinking

(E) underline the importance of even small density-dependent factors in regulating long-term population densities
in line with pre.thinking



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


7. In the passage, the author does all of the following EXCEPT:

Pre-thinking

Detail question

Let's evaluate the options


(A) cite the views of other biologists
p2

(B) define a basic problem that the passage addresses
P1

(C) present conceptual categories used by other biologists
P2

(D) describe the results of a particular study
A particular study is never mentioned

(E) draw a conclusion
P3/P4


------------------------------------------------------------------------------------------
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Re: As Gilbert White, Darwin, and others observed long ago, all [#permalink]
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