The pronghorn, an antelope-like mammal that lives on the western plain

Question

The pronghorn, an antelope-like mammal that
lives on the western plains of North America, is the
continent’s fastest land animal, capable of running 90
kilometers per hour and of doing so for several
  (5)   kilometers. Because no North American predator is
nearly fast enough to chase it down, biologists have
had difficulty explaining why the pronghorn
developed its running prowess. One biologist,
however, has recently claimed that pronghorns run as
  (10)   fast as they do because of adaptation to predators
known from fossil records to have been extinct for
10,000 years, such as American cheetahs and long-
legged hyenas, either of which, it is believed, were
fast enough to run down the pronghorn.

(15)   Like all explanations that posit what is called a
relict behavior—a behavior that persists though its only
evolutionary impetus comes from long-extinct environ-
mental conditions—this one is likely to meet with skep-
ticism. Most biologists distrust explanations positing relict
  (20)   behaviors, in part because testing these hypotheses is
so difficult due to the extinction of a principal component.
They typically consider such historical explanations
only when a lack of alternatives forces them to do so.
But present-day observations sometimes yield
  (25)   evidence that supports relict behavior hypotheses.

In the case of the pronghorn, researchers have
identified much supporting evidence, as several
aspects of pronghorn behavior appear to have been
shaped by enemies that no longer exist. For example,
  (30)   pronghorns—like many other grazing animals—roam
in herds, which allows more eyes to watch for predators
and diminishes the chances of any particular animal
being attacked but can also result in overcrowding
and increased competition for food. But, since
  (35)   pronghorns have nothing to fear from present-day
carnivores and thus have nothing to gain from herding,
their herding behavior appears to be another adaptation
to extinct threats. Similarly, if speed and endurance
were once essential to survival, researchers would
  (40)   expect pronghorns to choose mates based on these
athletic abilities, which they do—with female pronghorns,
for example, choosing the victor after male pronghorns
challenge each other in sprints and chases.

Relict behaviors appear to occur in other animals
  (45)   as well, increasing the general plausibility of such a
theory. For example, one study reports relict behavior
in stickleback fish belonging to populations that have
long been free of a dangerous predator, the sculpin.
In the study, when presented with sculpin, these
  (50)   stickleback fish immediately engaged in stereotypical
antisculpin behavior, avoiding its mouth and swimming
behind to bite it. Another study found that ground
squirrels from populations that have been free from
snakes for 70,000 to 300,000 years still clearly recognize
  (55)   rattlesnakes, displaying stereotypical antirattlesnake
behavior in the presence of the snake. Such fear,
however, apparently does not persist interminably.
Arctic ground squirrels, free of snakes for about
3 million years, appear to be unable to recognize the
  (60)   threat of a rattlesnake, exhibiting only disorganized
caution even after being bitten repeatedly.    1 
 1. Which one of the following most accurately states the main point of the passage?

(A) Evidence from present-day animal behaviors, together with the fossil record, supports the hypothesis that the pronghorn’s ability to far outrun any predator currently on the North American continent is an adaptation to predators long extinct.
(B) Although some biologists believe that certain animal characteristics, such as the speed of the pronghorn, are explained by environmental conditions that have not existed for many years, recent data concerning arctic ground squirrels make this hypothesis doubtful.
(C) Research into animal behavior, particularly into that of the pronghorn, provides strong evidence that most present-day characteristics of animals are explained by environmental conditions that have not existed for many years.
(D) Even in those cases in which an animal species displays characteristics clearly explained by long-vanished environmental conditions, evidence concerning arctic ground squirrels suggests that those characteristics will eventually disappear.
(E) Although biologists are suspicious of hypotheses that are difficult to test, there is now widespread agreement among biologists that many types of animal characteristics are best explained as adaptations to long-extinct predators.

2 
 2. Based on the passage, the term “principal component” (line 21) most clearly refers to which one of the following?

(A) behavior that persists even though the conditions that provided its evolutionary impetus are extinct
(B) the original organism whose descendants’ behavior is being investigated as relict behavior
(C) the pronghorn’s ability to run 90 kilometers per hour over long distances
(D) the environmental conditions in response to which relict behaviors are thought to have developed
(E) an original behavior of an animal of which certain present-day behaviors are thought to be modifications

3 
 3. The last paragraph most strongly supports which one of the following statements?

(A) An absence of predators in an animal’s environment can constitute just as much of a threat to the well-being of that animal as the presence of predators.
(B) Relict behaviors are found in most wild animals living today.
(C) If a behavior is an adaptation to environmental conditions, it may eventually disappear in the absence of those or similar conditions.
(D) Behavior patterns that originated as a way of protecting an organism against predators will persist interminably if they are periodically reinforced.
(E) Behavior patterns invariably take longer to develop than they do to disappear.

4 
 4. Which one of the following describes a benefit mentioned in the passage that grazing animals derive from roaming in herds?

(A) The greater density of animals tends to intimidate potential predators.
(B) The larger number of adults in a herd makes protection of the younger animals from predators much easier.
(C) With many animals searching it is easier for the herd to find food and water.
(D) The likelihood that any given individual will be attacked by a predator decreases.
(E) The most defenseless animals can achieve greater safety by remaining in the center of the herd.

5 
 5. The passage mentions each of the following as support for the explanation of the pronghorn’s speed proposed by the biologist referred to in line 8 EXCEPT:

(A) fossils of extinct animals believed to have been able to run down a pronghorn
(B) the absence of carnivores in the pronghorn’s present-day environment
(C) the present-day preference of pronghorns for athletic mates
(D) the apparent need for a similar explanation to account for the herding behavior pronghorns now display
(E) the occurrence of relict behavior in other species

6 
 6. The third paragraph of the passage provides the most support for which one of the following inferences?

(A) Predators do not attack grazing animals that are assembled into herds.
(B) Pronghorns tend to graze in herds only when they sense a threat from predators close by.
(C) If animals do not graze for their food, they do not roam in herds.
(D) Female pronghorns mate only with the fastest male pronghorn in the herd.
(E) If pronghorns did not herd, they would not face significantly greater danger from presentday carnivores.

sting8 · Accepted Answer

Option (D) in Q6 is a cleverly designed trap.

You can rule it out because of the extreme "only".

But, if you closely read the option you can clearly see the scope shift of the statement.

P3 states "with female pronghorns, for example, choosing the victor after male pronghorns challenge each other in sprints and chases."
This means female proghorns prefer winners of the race whenever some male proghorns  compete among each other  i.e. they prefer fastest among those who compete.

But option (D) suggests, they prefer to mate with the fastest in the herd. Fastest in the herd can be only one. If this option is true, then all females will mate with only one male proghorn. Thus, the meaning is completely altered.

EXAMPLE  
There are 5 male proghorns based on their speeds, P1 > P2 > P3 > P4 > P5
 What passage says 
Say, P3,P4,P5 compete. Then, P3 will win and females would choose to mate with P3
 What option says 
The fastest in the herd = P1
So, all females would choose to mate with P1

Sajjad1994 · Answer

Passage Summary

Each of the three sentences of  paragraph 1  has a reasonably clear purpose and adds something substantial to the foundation. Sentence 1 offers the Topic (the pronghorn) and the Scope (the animal’s incredible and unique running ability). Sentence 2 offers a question that puzzles scientists (i.e., “How did this critter get to be so fast?”), a strong suggestion that the author’s Purpose will be to come up with an answer. And sentence 3 indeed does offer one: a scientist thinks that today’s pronghorn inherited its speed from its early ancestors, who had to outrun nowextinct predators.

Such inheritance, we learn in  paragraph 2 , is called  “relict behavior,”  something about which many experts are perhaps understandably skeptical (how can you test such a theory when the predators are long gone?).  Paragraph 2  ends with a transitional sentence that takes us deftly from the skeptics’ position to the author’s view. When you read  lines 24–25 , you should’ve said to yourself,  “I bet I’m about to hear about some ‘present-day observations’ that support the pronghorn ‘relict behavior hypothesis.’”  Well, whether or not you predicted it, that’s what you get.

Other apparent examples of relict behavior in the pronghorn  (paragraph 3)  make it more likely that its extraordinary speed is yet another; and other examples in other mammals (stickleback fish and ground squirrels, respectively, in  paragraph 4 ) make relict behavior even more plausible. It was probably wise to bracket the fish and squirrel portions of paragraph 4 so as to locate each rapidly during your question work. A simple but effective Roadmap would look like so:

Paragraph 1:  Q. & proposed answer
 Paragraph 2:  Relict behavior; why it’s distrusted
 Paragraph 3:  Other r.b. in pronghorns
 Paragraph 4:  R.b. in other mammals

Sajjad1994 · Answer

Explanation

1. Which one of the following most accurately states the main point of the passage?

Difficulty Level:   Hard

Explanation

Only  (A)  reflects the author’s concern with explaining the amazing speed of the pronghorn by assembling support for the relict behavior hypothesis.

(B)  renders the Topic (the pronghorn) as an afterthought, while raising up the ground squirrel  (lines 52–61 only)  in importance. Worse,  (B)  thinks that the squirrel example casts doubt on the idea of relict behavior, when in fact  lines 52–56  support it.

(C) , like  (B) , treats the pronghorn as something of an afterthought instead of the passage’s principal concern. The author isn’t interested in making a gross generalization explaining  “most present-day characteristics of animals.”

(D)  makes the ground squirrel the passage’s star while ignoring the pronghorn altogether, and implies that the author’s main concern is with predicting future animal characteristics rather than explaining presentday ones.

(E)  goes too far in implying widespread expert agreement on the relict behavior hypothesis ( “most,”  we’re told,  “distrust”  it), and also veers too far from the Topic and Scope, namely the speed of the pronghorn.

Answer: A

Sajjad1994 · Answer

Explanation

3. The last paragraph most strongly supports which one of the following statements?

Difficulty Level:   Hard

Explanation

There are only two major ideas in  paragraph 4 : that other mammals besides the pronghorn exhibit apparent relict behavior  (lines 44–55) , and that some relict behavior may not be permanent  (lines 56–61) , as witness the Arctic ground squirrel who after 3 million snakeless years seems finally to have forgotten the threat that rattlers can pose. That last is the support for correct choice  (C) . The  “stereotypical rattlesnake behavior”  is the adaptation to the  “environmental conditions”  of the presence of rattlers, and that behavior did eventually disappear in the absence of the predators.

(A)  The absence of rattlesnake predators caused no threat to the squirrels’ well-being. It was only threatened when the snakes came back.

(B)  Relict behaviors  “appear to occur in other animals,”  says  line 44 , a far cry from their being found in  “most wild animals living today.”

(D)  A 180: although 3 million years is a long time, finally the squirrels’ unnecessary antirattlesnake behavior did go away; it proved not to  “persist interminably.”

(E)  No comparison between period of development and period of disappearance is ever suggested.

Answer: C

Sajjad1994 · Answer

Explanation

6. The third paragraph of the passage provides the most support for which one of the following inferences?

Difficulty Level:   Hard

Explanation

(E)  is essentially a straightforward paraphrase of  lines 35–36.  The pronghorns’ tendency to herd is perceived as relict behavior precisely because the creatures “have nothing to gain from herding.” Thus it is inferable that if the pronghorn ceased herding they’d still have  “nothing to fear from present-day carnivores.”  Most of us realize this after making our way confidently through the other, noninferable statements:

(A)  casts the pronghorn in the role of attacker, when in fact  paragraph 3  is about herding as a defensive maneuver. Whatever pronghorns do or do not prey on is irrelevant to the passage, and certainly to  paragraph 3.

(B)  contradicts the entire sense of  paragraph 3.  There are no predator threats: The pronghorns  “have nothing to fear from present-day carnivores.”  The whole point is that the pronghorns’ herding, despite there being no need to do so, is evidence of a relict behavior at work.

(C) ’s generalization is contradicted in  paragraph 3 , and the contrapositive of  (C)   (“If animals roam in herds, they graze for food”)  proves it, because  paragraph 3  makes clear that on the contrary,  “many…grazing animals…roam in herds…to watch for predators.”

(D)  distorts the sense of  lines 38–43.  Yes, the victor of each  “sprint or chase”  gets picked, but that victor is simply the fastest in that race and not necessarily  “the fastest in the herd.”

Answer: E

Sajjad1994 · Answer

Explanation

4. Which one of the following describes a benefit mentioned in the passage that grazing animals derive from roaming in herds?

Difficulty Level:   500

Explanation

Lines 29–34  describe the herding behavior, and the only benefits cited are that it  “allows more eyes to watch for predators and diminishes the chances of any particular animal being attacked.”  The latter is correct  choice (D).  Although herding might plausibly intimidate predators  (A) , protect the young  (B) , render sustenance easier to find  (C) , and shelter the defenseless in the herd’s midst  (E) , none of those factors is ever mentioned.

Answer: D

5. The passage mentions each of the following as support for the explanation of the pronghorn’s speed proposed by the biologist referred to in line 8 EXCEPT:

Difficulty Level:   600-650

Explanation

A variety of evidence for the proposed (relict behavior) explanation of the pronghorn’s speed is offered, beginning around  line 8.

Paragraph 1  mentions the fossils of now-extinct creatures  (A)  whose speed would have been enough to favor the development of speed in their pronghorn prey. In  paragraph 3 , we hear about two other apparent examples of relict behavior: the creatures’ unnecessary herding habit  (D)  and its curious mating habits that favor the swift  (C) .

And as for  paragraph 4 , well,  lines 44–46  explicitly tell us that the paragraph will be all about  (E) —the apparent relict behavior in stickleback fish and ground squirrels.

(B) , on the other hand, is a 180. There are plenty of carnivores in the pronghorn’s environment today. It’s just that the pronghorn has nothing to fear from them. Too fast, don’t you know  (lines 5–6).

Answer: B

nikitathegreat · Answer

GMATNinja   karishma  - Can you explain Q3.. confused between option choice C and D.
Also, how do we know that squirrels were earlier adapted to snakes and then there was absence of snakes and hence they have forgotten the adaptation?

GMATNinja · Answer

Question 3 
 
This is the kind of question that can feel like a maddening 50/50. The tiebreaker is the author's specific language choices.

Take another look at (C):

The word "may" should be jumping off the screen at you. You're right that we don't know with 100% certainty that these arctic squirrels adapted to rattlesnakes. But we know two things:

1) the rattlesnakes were around and the arctic ground squirrels didn't all get eaten and go extinct, so it suggests they had some kind of adaptive behavior in the past; otherwise, how would they have survived?

2) Other kinds of ground squirrels displayed adaptive behavior to rattlesnakes.

2) Other kinds of ground squirrels displayed adaptive behavior to rattlesnakes.

Taken together it certainly seems  possible  that the arctic ground squirrels adopted adaptive behaviors to rattlesnakes a very long time ago, only to see that behavior vanish over time.

Now go back to (D):

Interminably? As in, "forever?" How could we know that? Isn't it at least possible that newer patterns could replace the old?

So while (D) might be tempting, the language makes it less compelling than (C), which is our answer.

I hope that helps!

agrasan · Answer

Hi  GMATNinja

Can we also reject option D on the basis of reasoning that the conditional   "if they are periodically reinforced"   is not mentioned anywhere in the paragraph?

GMATNinja · Answer

Sure, there's no example of periodic reinforcement in the passage, so that's another reason to eliminate (D).

The pronghorn, an antelope-like mammal that lives on the western plain

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The pronghorn, an antelope-like mammal that lives on the western plain

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