Any species participates in what biologists call a "specific ecology,"

Question

Any species participates in what biologists call a "specific ecology," a relationship to its environment described by measurement of both environmental factors affecting the species and the species's response to these factors. Environmental factors include such variables as amount of light and abundance of food; species' responses typically include changes in the rates of birth, death, immigration, and emigration.

Since environmental stresses limit population growth, variations in environment correlate directly with variation in local species' population density. The relationships between particular environmental stresses and specific modes of response are difficult to define and predict; however, the relationship between the various response modes and changes in population density is relatively simple. The rate of change in population density is equal to the immigration rate plus the birth rate, minus the death rate, minus the emigration rate. Introduction of iodine into an area populated by sea urchins, for example, might affect the birth rate and immigration rate negatively, and the death rate and emigration rate positively, shifting the rate of change of population density toward the negative.    1 
 1. The purpose of this passage is to

A. question the existence of specific ecologies
B. reveal the effects of the introduction of iodine into a population of sea urchins
C. discuss the specific factors that limit sea urchin population growth
D. predict the relationships between various environmental factors and specific modes of response
E. define "specific ecology" and illustrate how local population density changes when certain factors are altered

2 
 2. The author discusses the introduction of iodine into a population of sea urchins in order to

A. question the usefulness of statistical approaches to ecology
B. illustrate how population density is affected by species' response modes
C. explain the concept of "specific ecology"
D. demonstrate how chemical pollutants affect a marine environment
E. show that population density remains constant over time despite environmental changes

3 
 3. It can be inferred that ecologists probably have the LEAST precise understanding of which of the following?

A. The relationship between variation in environment and variation in local population density
B. How species' response modes affect population density
C. The effect of introducing a toxin into an area on the immigration rate in the area
D. What types of behavior comprise species' responses to environmental stresses
E. The relationship between a given environmental stress and a given mode of response

4 
 4. It can be inferred that a given species's "specific ecology" would include which of the following factors?

I. The availability of food favored by the species
II. The number of predators present in the species's local environment
III. Increase in the birth rate due to favorable environmental conditions

A. I only
B. III only
C. I and II only
D. II and III only
E. I, II, and III

RC Butler 2021  -  Practice Two RC Questions Everyday.   
Passage # 282 Date: 16-Jul-2021
 This question is a part of RC Butler 2021 .  Click here for Details

kantapong · Answer

P1: Species & specific ecology
P2: Env. stress & response (detail to P1)

Q1 Purpose
A. question the existence of specific ecologies (no - assume it exists)
B. reveal the effects of the introduction of iodine into a population of sea urchins (no - too narrowed)
C. discuss the specific factors that limit sea urchin population growth (no - too narrowd)
D. predict the relationships between various environmental factors and specific modes of response (no - not predict; unsupported)
E. define "specific ecology" and illustrate how local population density changes when certain factors are altered (yes - define specific ecology in P1 and how local pop density changes in P2)
Ans: E

Q2 sea urchin as an EXAMPLE
A. question the usefulness of statistical approaches to ecology (no - unsupported)
B. illustrate how population density is affected by species' response modes (YES)
C. explain the concept of "specific ecology" (no - just a part of specific ecology)
D. demonstrate how chemical pollutants affect a marine environment (no - too narrow)
E. show that population density remains constant over time despite environmental changes (no - contradict)
Ans: B

Q3 LEAST precise understanding: env stress & species response
A. The relationship between variation in environment and variation in local population density
B. How species' response modes affect population density
C. The effect of introducing a toxin into an area on the immigration rate in the area
D. What types of behavior comprise species' responses to environmental stresses
E. The relationship between a given environmental stress and a given mode of response (YES)
Ans: E

Q4 Infer
I. The availability of food favored by the species (YES - abundance of food)
II. The number of predators present in the species's local environment (YES - environmental factor)
III. Increase in the birth rate due to favorable environmental conditions (YES - species response)
A. I only
B. III only
C. I and II only
D. II and III only
E. I, II, and III

Ans: E

Ankit2801 · Answer

Q3 LEAST precise understanding: env stress & species response
A. The relationship between variation in environment and variation in local population density
B. How species' response modes affect population density
C. The effect of introducing a toxin into an area on the immigration rate in the area
D. What types of behavior comprise species' responses to environmental stresses
E. The relationship between a given environmental stress and a given mode of response

Could you please explain the answer?

Sajjad1994 · Answer

Welcome to GMAT Club!

Official Explanation

3. It can be inferred that ecologists probably have the LEAST precise understanding of which of the following?

Difficulty Level:   650

Explanation

Analyze the Question Stem:

The word  “inferred”  makes it clear that this is an Inference question.

Research the Relevant Text:

Note that the question asks about what ecologists have the LEAST precise understanding of. Use this as a clue - find in the passage where doubt or difficulty was expressed. The third paragraph states that  “The relationships between particular environmental stresses and specific modes of response are difficult to define and predict."  This could be, though doesn't have to be, a clue to the supported inference.

Make a Prediction:

The correct answer may refer to the relationships between stress and response.

Evaluate the Answer Choices:

(E)  refers to the relationship predicted and is the correct answer.

(A)  is incorrect because the second paragraph of the passage states that  "variations in environment correlate directly with variation in local species' population density."

(B)  is wrong because the calculation of the change in population density is described in detail in the third sentence of  paragraph two.

The main point of  (C)  is apparently well understood, since the hypothetical example of the sea urchins involves the effect of introducing iodine, presumably a toxin for sea urchins

(D)  is incorrect because the types of behavioral responses are described in the final sentence of the  first paragraph.

Answer: E

TAKEAWAY:  When an Inference question provides enough information to narrow down the subject matter of the inference, you may be able to use that information to make a prediction.

VerbalBot · Answer

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Any species participates in what biologists call a "specific ecology,"

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Any species participates in what biologists call a "specific ecology,"

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