Determining whether a given population of animals constitutes

Question

Determining whether a given population of animals constitutes a distinct species can be difficult because no single accepted definition of the term exists. One approach, called the biological species concept, bases the definition on reproductive compatibility. According to this view, a species is a group of animals that can mate with one another to produce fertile offspring but cannot mate successfully with members of a different group. Yet this idea can be too restrictive. First, mating between groups labeled as different species (hybridization), as often occurs in the canine family, is quite common in nature. Second, sometimes the differences between two populations might not prevent them from interbreeding, even though they are dissimilar in traits unrelated to reproduction; some biologists question whether such disparate groups should be considered a single species. A third problem with the biological species concept is that investigators cannot always determine whether two groups that live in different places are capable of interbreeding.

When the biological species concept is difficult to apply, some investigators use phenotype, an organism’s observable characteristics, instead. Two groups that have evolved separately are likely to display measurable differences in many of their traits, such as skull size or width of teeth. If the distribution of measurements from one group does not overlap with those of another, the two groups might reasonably be considered distinct species.

(Book Question: 54)
1. The passage is primarily concerned with

(A) describing the development of the biological species concept
(B) responding to a critique of reproductive compatibility as a criterion for defining a species
(C) considering two different approaches to identifying biological species
(D) pointing out the advantage of one method of distinguishing related species
(E) identifying an obstacle to the classification of biological species

(Book Question: 55)
2. The author of the passage mentions “groups that live in different places” (in line 21) most probably in order to

(A) point out a theoretical inconsistency in the biological species concept
(B) offer evidence in support of the biological species concept
(C) identify an obstacle to the application of the biological species concept
(D) note an instance in which phenotype classification is customarily used
(E) describe an alternative to the biological species concept

(Book Question: 56)
3. With which of the following statements regarding the classification of individual species would the author most likely agree?

(A) Phenotype comparison may help to classify species when application of the biological species concept proves inconclusive.
(B) Because no standard definition exists for what constitutes a species, the classification of animal populations is inevitably an arbitrary process.
(C) The criteria used by biologists to classify species have not been based on adequate research.
(D) The existence of hybrids in wild animal species is the chief factor casting doubt on the usefulness of research into reproductive compatibility as a way of classifying species.
(E) Phenotype overlap should be used as the basic criterion for standardizing species classification.

(Book Question: 57)
4. Which of the following best describes the function of lines 10-13 [First, mating between groups labeled as different species (hybridization), as often occurs in the canine family, is quite common in nature.]?

(A) It elaborates the definition of the biological species concept given in a previous sentence.
(B) It develops a point about the biological species concept made in the previous sentence.
(C) It states the author’s central point about the biological species concept.
(D) It identifies a central assumption underlying the biological species concept.
(E) It demonstrates why the biological species concept is invalid.

Show Spoiler

JOURNAL ARTICLE
The Problematic Red Wolf
Robert K. Wayne and John L. Gittleman
Scientific American
Vol. 273, No. 1 (JULY 1995), pp. 36-39
Published by: Scientific American, a division of Nature America, Inc.
https://www.jstor.org/stable/24981449
Page Count: 6

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Show Answer Question #1

Official Answer

C

Show Answer Question #2

Official Answer

C

Show Answer Question #3

Official Answer

A

Show Answer Question #4

Official Answer

B

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Lucy Phuong · Accepted Answer

Hi, I chose the right answer, so I hope that my experience may help.

This is a purpose question. It asks the function of particular lines 10-13:

"First, mating between groups labeled as different species (hybridization), as often occurs in the canine family, is quite common in nature."

---> The above sentence introduces the first among some disadvantages of biological species concept. 
Now we assess 5 options

A. It elaborates the definition of the biological species concept given in a previous sentence.  
No. Definition of this concept is already mentioned before, in lines 4-5 of the passage. OUT

B. It develops a point about the biological species concept made in the previous sentence. 
Hm. Let's see what the previous sentence says - "Yet this idea can be too restrictive". We can see clearly that this sentence is an introduction about limitations of the biological species concept, and the sentence in line 10-13 elaborates on the first negative point of its limitation. CORRECT

C. It states the author's central point about the biological species concept.  
If the question asked about function of this sentence "Yet this idea can be too restrictive", then answer might be yes. But in fact, the following sentence, which introduces the first disadvantage of the concept, is the one we have to look at. OUT.

D. It identifies a central assumption underlying the biological species concept.  
No, it's not. It just simply provides details of the first flaw of the concept. OUT.

E. It demonstrates why the biological species concept is invalid.  
To me, this option could be considered a runner-up. The reason why this option is incorrect might be its inappropriate word choice "invalid". When a method is invalid, it might be regarded as no value and we should not use it at all, but this is not necessarily true in the case of biological species concept. According to author, "this idea can be too restrictive". Therefore, we may understand that in general, the concept has some values, but IN SOME CASES, it seems not to be effective as expected.

That's my reasoning. Hope it will help. Just respond if you have any further concern.

GMATNinja · Answer

I agree that the wording of (C) is a bit confusing! Here's why the word "biological" isn't a great reason to eliminate (C):

The passage explores two methods to determine "whether a given population of animals constitutes a  distinct  species." These methods are:
  "the biological species concept" and 
 "phenotype."

So, we know that the two approaches can be used to determine whether a given population constitutes a " distinct  species", but aren't told whether that's the same thing as a " biological  species," as specified in answer choice (C). Can we infer that these two terms mean the same thing?

If we want to eliminate (C), we have to assume that "distinct species" and "biological species" refer to two different things. Nothing in the passage suggests that these two things are different... sure, one method has "biological" in the name, but we know that both methods are used to determine the same thing. To illustrate that idea, consider the following:

In order to track revenue, a company can utilize either cash-basis accounting or accrual accounting. 
 Even though only one of the two methods has the word "accrual" in it, we could still say that both methods can be used to track how much revenue a company  accrues  each year. 
 Similarly, even though only one of the methods described in the passage has the word "biological" in the name, doesn't mean that the other can't also be used to identify  biological  species.

So even though the word "biological" in choice (C) is very confusing, it's not a good enough reason to eliminate (C). In fact, saying, "... two different approaches to identifying  biological  species" is no different than saying, "... two different approaches to identifying species  of living organisms " ("biological" simply means "related to living organisms").

Choice (C) might not  look  good, but, using POE, it is the  best  answer.

I hope that helps!

jaisonsunny77 · Answer

(1) The passage is primarily concerned with

In the first paragraph, one way to define/identify species distinction is suggested and three reasons are given explaining why this particular method (way) may not be feasible. In the second paragraph, a different method/concept is suggested that people can use in order to determine ''distinction'' among species. Hence, we can reasonably infer that the main idea of the passage is to highlight two different approaches to determining ''distinction'' among species.

This school of thought is perfectly reflected in (C).

(C) considering two different approaches to identifying biological species

Hence,   (C) is the right answer choice.  
 
  (2) The author of the passage mentions “groups that live in different places” (in line 21) most probably in order to 
 
if you read the whole sentence that contains this highlighted text, we have "A third problem with the biological species concept is that investigators cannot always determine whether two groups that live in different places are capable of interbreeding". From this entire sentence, we can reasonably infer that the highlighted text is a part of a reason that explains why biological species concept to determine species ''distinction'' may not be feasible. This thought is perfectly reflected in (C)

(C) identify an obstacle to the application of the biological species concept

Hence,   (C) is the right answer choice.  
 
  (3) With which of the following statements regarding the classification of individual species would the author most likely agree? 
 
 In the first line of the second paragraph, we have ''When the biological species concept is difficult to apply, some investigators use phenotype, an organism’s observable characteristics, instead''. This would reflect what (A) mentions perfectly.

(A) Phenotype comparison may help to classify species when application of the biological species concept proves inconclusive.

Hence,   (A) is the right answer choice.  
 
  (4) Which of the following best describes the function of lines 10-13  ? 
 
If you read the sentence prior to the highlighted sentence of the first paragraph, you can see that the ''three reasons'' that follows this key sentence actually supports the idea/assertion made in this key sentence (where the key sentence is "Yet this idea can be too restrictive"). This is exactly what (B) mentions

(B) It develops a point about the biological species concept made in the previous sentence.

Hence,   (B) is the right answer choice.

GMATNinja · Answer

Passage breakdown 
In the first paragraph (P1), the author:

Introduces a difficulty: how to determine whether a group of animals constitutes a distinct species. 
 Discuss one method to address this issue. 
 Outlines three problems with this method.

In the second paragraph, the author:

Introduces a second method. 
 Explains how this method could work when the first method fails.

For more on the process of breaking down RC passages, check out  this article  and  our live RC videos .

Explanations for individual questions 
  Question 1
 
  Part 1  
  Part 2    
  Question 2  
 Question 3
 
  Part 1  
  Part 2

Minakshi20 · Answer

Why answer choice C is not the right answer. Can anyone explain why B over C?
Which of the following best describes the function of lines 10-13?
A. It elaborates the definition of the biological species concept given in a previous sentence.
B. It develops a point about the biological species concept made in the previous sentence.
C. It states the author???s central point about the biological species concept.
D. It identifies a central assumption underlying the biological species concept.
E. It demonstrates why the biological species concept is invalid.

kannu44 · Answer

When the biological species concept  is difficult to apply,  some investigators use phenotype, an (25) organism’s observable characteristics, instead.

i third question answer is . Phenotype comparison may help to classify species when application of the biological species concept proves inconclusive.

Here inconclusive and difficult to apply has been taken for same meaning although it differs.

I rejected the option for the same difference .

can anyone help.
thanks

GMATNinjaTwo · Answer

Consider the second example cited in the first paragraph:

Even though the two populations can interbreed, we would not be able to definitively conclude that we have two species. Thus, although not directly stated in the passage, we can infer that using the biological species concept would prove inconclusive in that case.

Choice (A) is the best answer to the third question.

Sakshamachiever · Answer

Hi Experts,
In Q1. The passage is primarily concerned with

A. describing the development of the biological species concept
B. responding to a critique of reproductive compatibility as a criterion for defining a species
C. considering two different approaches to identifying biological species
D. pointing out the advantage of one method of distinguishing related species
E. identifying an obstacle to the classification of biological species

I am confused between B and C.While reading the passage,the focus was on drawbacks of biological species concept (based on reproductive compatibility) and towards the end an alternative was described.So I chose B.
Can anyone explain why this is incorrect ?

GMATNinja · Answer

Question 1 
 
As for choice (B), the author does present several possible critiques of reproductive compatibility as a criterion for defining a species, but the passage is not concerned with  responding  to those possible critiques.

Rather, the author presents those drawbacks to illustrate situations in which the biological species concept is difficult to apply. The author then presents an alternative (phenotype) that can be used in such situations. The author does not say that the biological species concept should be abandoned in favor of phenotype. Instead, the author simply notes that some investigators use the latter when the biological species concept is difficult to apply.

The author considers both approaches but is not primarily concerned with defending or rejecting either. So, choice (C) is more appropriate.

I hope that helps!

Sakshamachiever · Answer

Hi  GMATNinja ,
Thanks for your response and it helped me to understand why B) is incorrect.
I agree that the author does not respond to a critique.Just to confirm if it was a response to a critique ,the author would have stated his opinion regarding criticism of this theory,correct ?

Also,for understanding sake,can you confirm the following ?

You mentioned that
 The author then presents an alternative (phenotype) that can be used in such situations. The author does not say that the biological species concept should be abandoned in favor of phenotype. Instead, the author simply notes that some investigators use the latter when the biological species concept is difficult to apply.

The author considers both approaches but is not primarily concerned with defending or rejecting either. Thus, choice (C) is more appropriate .

Below are my comments:

But doesn't the author's way of transitioning from the drawbacks of one theory (say theory 1) to a theory (say theory 2) which can resolve the issue in theory 1 without specifying any drawbacks of theory 2 suggest a preference for theory 2 ?

Also,the author's main aim is to Determinine whether a given population of animals
constitutes a distinct species .
At the end he says using theory 2 that 
If the distribution of measurements from one group does not overlap with those of another, the two groups might reasonably be considered distinct species.

Doesn't this clearly show that theory 2 is the winner here ?

Thanks,
Saksham.

jawele · Answer

Hi,

Could anybody help me out with (Book Question: 55)
The author of the passage mentions “groups that live in different places” (in line 21) most probably in order to

A. point out a theoretical inconsistency in the biological species concept
B. offer evidence in support of the biological species concept
C. identify an obstacle to the application of the biological species concept
D. note an instance in which phenotype classification is customarily used
E. describe an alternative to the biological species concept

Although I chose the correct answer, I'm still in doubt about A. Do the words in line 20 '...that investigators  cannot always  determine whether...' show why this answer choice is incorrect, i.e. the underlined words actually point to an inconsistency in practice, and not in theory?

Thank you

GMATNinja · Answer

Question 2 
 
 jawele , that's right! Choice (A) represents a PRACTICAL challenge. According to the biological species concept, a species is a group of animals that can mate with one another but not with members of a different group. The text in lines 20-21 describes the third problem with this approach. Even though in theory this criteria might help us determine whether two groups belong to the same species, if the groups live in different places, there is no way to determine whether they can interbreed. Thus, even though the criteria might make sense in theory, we cannot practically apply it.

Choice (C) is a better answer.

GMATNinja · Answer

Even if the author had a preference for "theory 2", choice (B) would not be appropriate. The author PRESENTS criticisms of the biological species concept. RESPONDING to criticisms would involve citing criticisms (made by others) and DEFENDING the biological species concept against those criticisms. For example:

Responding to criticisms that she was weak on crime, the mayor pointed out that crime rates have decreased by 5% every year since she took office.

Furthermore, the author only suggests that theory 2 is "the winner" in  certain  situations. This does not necessarily imply that the author favors one over the other. For example, Medicine X might be great for lowering cholesterol MOST of the time. However, under certain circumstances, it might be better to prescribe Medicine Y. That doesn't make Y better than X, it just means that Y is better in SOME cases.

Similarly, the author states that theory 2 can be used "when the biological species concept is difficult to apply." This does not suggest that theory 2 is better. It simply suggests that there is an alternative that can be used in situations when the biological species concept is not appropriate (i.e. when the drawbacks described would make it inaccurate).

Regardless, the author is not "responding to a critique" of the biological species concept, so choice (B) should be eliminated.

pratiknayan10 · Answer

Can anyone please explain why option c in question 3 is wrong. 
In the opening line it is mentioned that no single definition of the term exists. Is "Arbitary process" a too far interpretation of the same.
Kindly help

GMATNinja · Answer

I believe you're referring to choice (B):

And yes, you're on the right track. The second half of this statement does not reflect what the author has written.

If the classification of animal populations were  inevitably an arbitrary process , then no matter what scientists may try, we wouldn't expect them to ever classify animal populations in a consistent way. Yet, in the second paragraph, the author suggests that phenotype comparison might reasonably be used to group animals into distinct species.

These two statements don't match, so we eliminate (B). On the other hand, choice (A) is almost a perfect rephrasing of what the author has written.

I hope this helps!

NinetyFour · Answer

For Q3) Could someone explain how A is correct? In the passage the author clearly writes: "When the biological species concept is difficult to apply, some investigators use phenotype".

Difficult to apply  does not mean  inconclusive , so how does A make sense?

I chose D because the author writes "yet this idea can be too restrictive. First, mating between groups labeled as different species (hybridization), as often occurs in the canine family, is quite common in nature"

I understand that in D the answer says hybridization is THE way of undermining the biological species concept, but this phrasing seems to be more valid than A. Could someone explain where my thinking went wrong?

GMATNinja

GMATNinja · Answer

kchen1994 , please see  this  post for an analysis on "difficult to apply" vs. "inconclusive" for answer choice (A).

As for answer choice (D), you are on the right track. Here is the exact wording of that answer choice:

The author mentions three separate issues with using reproductive compatibility as the basis for defining species. The author never says that one or another of those factors is more important than the others, so there is an issue with the word "chief" in the answer choice. You can eliminate answer (D) for that reason.

I hope this helps!

MAnkur · Answer

I rejected the option C and picked B for the word "Biological" assuming that it is not supported by the passage and first line of the passage says about the species and not just the biological species,

While reviewing I could eliminate B more than C!

Any tips on how to avoid such mistakes - not over-using one word off or too extreme concept

Experts may please respond!

GMATNinja · Answer

I think you answered your own question! The key is to use process of elimination every time and to avoid prematurely eliminating options. If you know why it is wrong, eliminate it. But if you aren't quite sure what a choice means, leave it. If you are uncomfortable with a single word but not sure whether it's a deal-breaker, leave it.

For a broader discussion of RC technique, check out our  RC guide for beginners .

I hope this helps!

Determining whether a given population of animals constitutes

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Determining whether a given population of animals constitutes

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