In terrestrial environments, gravity places special demands

AjiteshArun did a nice job clearing up the issues on questions #4 and #6, but it looks like there's plenty of pain on question #8. So here's that one again:





As with all "primarily concerned" questions, we should establish the overall purpose of the passage. This is different from seeking an answer choice that seems to add up individual pieces of the passage. So why did the author write this thing?

• The author wrote paragraph 1 to introduce the adaptations that terrestrial snakes have made in response to the demands of gravity.
• The author wrote paragraph 2 to explain how gravity on land leads to circulatory failure, by comparing the circulation and blood pressure of terrestrial snakes to sea snakes
• The author wrote paragraph 3 to illustrate the specific circulation-aiding adaptations of terrestrial snakes, by describing different examples of these adaptations.

When we follow the author's purpose from paragraph to paragraph, we see that the author wrote this passage to explain how the adaptations of terrestrial snakes help those snakes circulate blood -- and consequently, survive -- in terrestrial environments.

Remember that in these question types, wrong answer choices will often distract us by stating something that's probably true, and maybe very important to the passage. That's not the same thing as stating why the author wrote the passage as a whole.


This looks good! It fits our understanding of the author's purpose (to explain adaptations of terrestrial snakes), and doesn't add any erroneous details regarding what that explanation says. Let's keep (A) around and review our other choices.


This is more like a description of what the author is doing in paragraph 2 (and doesn't really get at the purpose of that paragraph, either). Eliminate (B).


This is misleading. Sure, the author explains why the circulatory system differs (gravity works differently in water than on land). But when the author sat down and decided that it was necessary to write this passage, was she thinking, "I have to tell everyone why the circulatory systems of these two snakes are different"?

Not exactly. Choice (C) makes it seem like the author's main purpose is the comparison of two classes of snake. In fact, the author is primarily concerned with explaining how the terrestrial snake adapts to terrestrial gravity. The sea snake only appears as an example to show the particular demands of terrestrial gravity, and how terrestrial adaptations help terrestrial snakes meet those demands. That's why we eliminate (C).


The author isn't making a judgment on which snake's cardiovascular system is better or worse than the other. Eliminate (D).


This is totally off-track. The author's focus is the terrestrial snake, and how the terrestrial snake neutralizes these effects in terrestrial environments. Eliminate (E).

This is why (A) remains the best answer. We do see something that seems true in every other answer choice, but we can eliminate choices (B), (C), (D), and (E) because none of them express the overall purpose of the passage.

I hope this helps!
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One such adaptation is the closer proximity of the terrestrial snake's heart to its head, which helps to ensure circulation to the brain, regardless of the snake's orientation in space. The heart of sea snakes can be located near the middle of the body, a position that minimizes the work entailed in circulating blood to both extremities. In arboreal snakes, however, which dwell in trees and often assume a vertical posture, the average distance from the heart to the head can be as little as 15 percent of overall body length. Such a location
requires that blood circulated to the tail of the snake travel a greater distance back to the heart, a problem solved by another adaptation. When climbing, arboreal snakes often pause
momentarily to wiggle their bodies, causing waves of muscle contraction that advance from the lower torso to the head. By compressing the veins and forcing blood forward, these contractions apparently improve the flow of venous blood returning to the heart.


in the chain of the argument we have TWO shifts..............hope this helps
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#24 - D

I got this one wrong. I narrowed down to A and D.

I chose A because the end of the 2nd paragraph only mentions one phenomena, namely blood pressure at their midpoint drops significantly.

What in bloody name is the 2nd phenomena?

I chose A.

In the passage,the author is primarily concerned with doing which of the following?
(A) Explaining adaptations that enable the terrestrial snake to cope with the effects of gravitational pressure on its circulatory system
(B) Comparing the circulatory system of the sea snake with that of the terrestrial snake
(C) Explaining why the circulatory system of the terrestrial snake is different from that of the sea snake
(D) Pointing out features of the terrestrial snake's cardiovascular system that make it superior to that of the sea snake
(E) Explaining how the sea snake is able to neutralize the effects of gravitational pressure on its circulatory system

For this question, I got confused between A & C. I choose E but OA is A.

Official Guide says " The passage is more concerned with how the system of two snakes are different, rather than why, in order to identify how terrestrial snakes have adapted to gravity's influence.

But passage has below line "That many terrestrial snakes in similar spatial orientations do not experience this kind of circulatory failure suggests that certain adaptations enable them to regulate blood pressure more effectively in those orientations."

It does talk about "why"

Can some expert throw some light on this evolutionary process
PS. I mean expert in RC and not expert in evolutionary process . Just kidding everyone is welcome to share their views

The primary purpose of the third paragraph is to
(A) introduce a topic that is not discussed earlier in the passage
(B) describe a more efficient method of achieving an effect discussed in the previous paragraph
(C) draw a conclusion based on information elaborated in the previous paragraph
(D) discuss two specific examples of phenomena mentioned at the end of the previous paragraph
(E) introduce evidence that undermines a view reported earlier in the passage

Why is D the correct answer?
To what 2 phenomena's is this option referring?

My answers and explanations:

1. The passage provides information in support of which of the following assertions?

(A) The disadvantages of an adaptation to a particular feature of an environment often outweigh the advantages of such an adaptation.
Not okie

(B) An organism's reaction to being placed in an environment to which it is not well adapted can sometimes illustrate the problems that have been solved by the adaptations of organisms indigenous to that environment
okie

(C) The effectiveness of an organism's adaptation to a particular feature of its environment can only be evaluated by examining the effectiveness with which organisms of other species have adapted to a similar feature of a different environment.
Similar feature …. Not okie, other species – not okie

(D) Organisms of the same species that inhabit strikingly different environments will often adapt in remarkably similar ways to the few features of those environments that are common.
similar ways – not okie

(E) Different species of organisms living in the same environment will seldom adapt to features of that environment in the same way.
Different species – not okie

2. According to the passage, one reason that the distribution of blood in the sea snake changes little while the creature remains in the ocean is that

Because the vertical pressure gradients within the blood vessels are counteracted by similar pressure gradients in the surrounding water

(A) the heart of the sea snake tends to be located near the center of its body
Not okie
(B) pressure gradients in the water surrounding the sea snake counter the effects of vertical pressure gradients within its blood vessels
okie
(C) the sea snake assumes a vertical posture less frequently than do the terrestrial and the arboreal snake
not okie
(D) the sea snake often relies on waves of muscle contractions to help move blood from the torso to the head
not okie

(E) the force of pressure gradients in the water surrounding the sea snake exceeds that of vertical pressure gradients within its circulatory system
Not okie

3. It can be inferred from the passage that which of the following is true of species of terrestrial snakes that often need to assume a vertical posture?
Explanation:
One such adaptation is the closer proximity of the terrestrial snake's heart to its head, which helps to ensure circulation to the brain, regardless of the snake's orientation in space. The heart of sea snakes can be located near the middle of the body, a position that minimizes the work entailed in circulating blood to both extremities. In arboreal snakes, however, which dwell in trees and often assume a vertical posture, the average distance from the heart to the head can be as little as 15 percent of overall body length

(A) They are more likely to be susceptible to circulatory failure in vertical postures than are sea snakes.
Not okie
(B) Their hearts are less likely to be located at the midpoint of their bodies than is the case with sea snakes.
okie
(C) They cannot counteract the pooling of blood in lower regions of their bodies as effectively as sea snakes can.
Not okie
(D) The blood pressure at their midpoint decreases significantly when they are tilted with their heads up.
Not okie
(E) They are unable to rely on muscle contractions to move venous blood from the lower torso to the head.
Not okie

4. The author describes the behavior of the circulatory system of sea snakes when they are removed from the ocean (see lines 17-20) primarily in order to

(A) illustrate what would occur in the circulatory system of terrestrial snakes without adaptations that enable them to regulate their blood pressure in vertical orientations
okie
(B) explain why arboreal snakes in vertical orientations must rely on muscle contractions to restore blood pressure to the brain

(C) illustrate the effects of circulatory failure on the behavior of arboreal snakes

(D) illustrate the superiority of the circulatory system of the terrestrial snake to that of the sea snake
Not okie
(E) explain how changes in spatial orientation can adversely affect the circulatory system of snakes with hearts located in relatively close proximity to their heads
Not okie

5. It can be inferred from the passage that which of the following is a true statement about sea snakes?
Explanation:
When removed from the water and tilted at various angles with the head up, however, blood pressure at their midpoint drops significantly, and at brain level falls to zero

(A) They frequently rely on waves of muscle contractions from the lower torso to the head to supplement the work of the heart.
Not okie
(B) They can not effectively regulate their blood pressure when placed in sea water and tilted at an angle with the head pointed downward.
Not okie ???
(C) They are more likely to have a heart located in close proximity to their heads than are arboreal snakes.
Not okie
(D) They become acutely vulnerable to the effects of gravitational pressure on their circulatory system when they are placed in a terrestrial environment.
okie
(E) Their cardiovascular system is not as complicated as that of arboreal snakes.
Not okie

6. The author suggests that which of the following is a disadvantage that results from the location of a snake's heart in close proximity to its head?

explanation: Such a locationrequires that blood circulated to the tail of the snake travel a greater distance back to the heart,

(A) A decrease in the efficiency with which the snake regulates the flow of blood to the brain
Not okie
(B) A decrease in the number of orientations in space that a snake can assume without loss of blood flow to the brain
Not okie
(C) A decrease in blood pressure at the snake's mid point when it is tilted at various angles with its head up
Not okie
(D) An increase in the tendency of blood to pool at the snake's head when the snake is tilted at various angles with its head down
Not okie
(E) An increase in the amount of effort required to distribute blood to and from the snake's tail
okie


7. The primary purpose of the third paragraph is to

(A) introduce a topic that is not discussed earlier in the passage
Not okie
(B) describe a more efficient method of achieving an effect discussed in the previous paragraph
okie
(C) draw a conclusion based on information elaborated in the previous paragraph
not okie, not conclusion
(D) discuss two specific examples of phenomena mentioned at the end of the previous paragraph
okie – choose – D is better than B
(E) introduce evidence that undermines a view reported earlier in the passage
not okie

8. In the passage,the author is primarily concerned with doing which of the following?

(A) Explaining adaptations that enable the terrestrial snake to cope with the effects of gravitational pressure on its circulatory system
okie
(B) Comparing the circulatory system of the sea snake with that of the terrestrial snake
Not okie
(C) Explaining why the circulatory system of the terrestrial snake is different from that of the sea snake
Not okie
(D) Pointing out features of the terrestrial snake's cardiovascular system that make it superior to that of the sea snake
Not okie, “explain the adaptation” is better
(E) Explaining how the sea snake is able to neutralize the effects of gravitational pressure on its circulatory system
Not enough information  wrong

Take a look at this part of the passage:

If the heart is closer to the head, the brain gets blood even against gravity (vertical posture). But that means that blood going to the tail needs to travel a greater distance. The passage calls this a "problem". So there is a problem/disadvantage resulting from "the location of a snake’s heart in close proximity to its head".

Now, because we already know that a position "near the middle" minimizes the work involved in circulating blood, we can say that more effort is needed to get blood to the tail if the heart is positioned closer to the head.
_________________

I do not understand the rationale behind the answer for Q8 (primary concern, General question).

In my opinion, both A and B are considered partial. A fails to mention sea snakes (which constitutes the whole 2nd paragraph) while B does not state gravity.
Why does OG prefer A than B, considering both are equally flawed?

gmatretest

If you observe clearly whole passage is about terrestrial snakes and their behavior is explained thorough the examples of sea snakes and arboreal snakes. So A covers the main point.

B strictly covers partial scope of the passage leaving out the main point. sea snakes and their circulation system is never the main aspect of the passage.

I hope this helps

The OG says it's an "application" question.

It states: "This question requires recognizing a principle underlying the passage's overall discussion. etc."

And here is what OG says about "application" questions in general:
"These questions measure your ability to discern the relationship between situations or ideas presented by the author and other situations or ideas that might parallel those in the passage."
"Unlike inference questions, application questions use ideas or situations not taken from the passage. Ideas and situations given in a question are like those given in the passage, and they parallel ideas and situation sin the passage."

Hope this helps!

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This passage took me 12 minutes. Just under 4 minutes for my Passage Map and TSP, and about 1 minute per question. Got 7/8. Failed on "The primary purpose of the third paragraph is to". I was lazy and should taken 20 seconds to reread the part of the passage.

hello
can you please shed light on the question below. I could not find two specific examples in the text. thank you! D

The primary purpose of the third paragraph is to
(A) introduce a topic that is not discussed earlier in the passage
(B) describe a more efficient method of achieving an effect discussed in the previous paragraph
(C) draw a conclusion based on information elaborated in the previous paragraph
(D) discuss two specific examples of phenomena mentioned at the end of the previous paragraph
(E) introduce evidence that undermines a view reported earlier in the passage

The last sentence of the second paragraph refers to "certain adaptations" that enable terrestrial snakes to regulate blood pressure more effectively when tilted at various angles. These adaptations, as described in the third paragraph, include: 1) the closer proximity of the terrestrial snake's heart to its head and 2) the ability of arboreal snakes to wiggle their bodies, causing waves of muscle contractions that apparently improve the flow of venous blood returning to the heart.

I hope that helps!
_________________

The main purpose of the passage is to talk about the adaptations of terrestrial snakes. The whole discussion around sea snakes is just an example ("The problem confronting terrestrial snakes is best illustrated by what happens to sea snakes...") to help us understand something about terrestrial snakes.
_________________

The author describes the behavior of the circulatory system of sea snakes when they are removed from the ocean (see lines 17-20) primarily in order to
(A) illustrate what would occur in the circulatory system of terrestrial snakes without adaptations that enable them to regulate their blood pressure in vertical orientations
(B) explain why arboreal snakes in vertical orientations must rely on muscle contractions to restore blood pressure to the brain
(C) illustrate the effects of circulatory failure on the behavior of arboreal snakes
(D) illustrate the superiority of the circulatory system of the terrestrial snake to that of the sea snake
(E) explain how changes in spatial orientation can adversely affect the circulatory system of snakes with hearts located in relatively close proximity to their heads

I got the answer as D.


When removed from the water and tilted at various angles with the head up, however, blood pressure at their midpoint drops significantly, and at brain level falls to zero. That many terrestrial snakes in similar spatial orientations do not experience this kind of circulatory failure suggests that certain adaptations enable them to regulate blood pressure more effectively in those orientations.

In this it is inferred that terrestrial snakes have certain adaptations which tells they are superior to sea snake.
Please explain why I might be wrong.

Thanks in advance

It's not as if the adaptions of terrestrial snakes are always better than those of sea snakes. Sure, if you take sea snakes out of their natural habitat, their adaptations will lead to a lot of problems. But then we should also ask what would happen if terrestrial snakes were to be put in the habitat of sea snakes!

We should look at it as: the adaptions of terrestrial snakes are suited to their (terrestrial) environment. To understand these adaptations, let's take a look at what happens to sea snakes when they are taken out of their environment and put in the environment of terrestrial snakes. But we should not conclude that the adaptions (including the circulatory system) of terrestrial snakes are superior to those of sea snakes generally.
_________________

P1 - Gravity is a B**** for cardiovascular systems. ex snake.
p2 - similar case given. sea snake.
p3 - adaptation, head close to heart. other snakes.

--------------------------------------
1. The passage provides information in support of which of the following assertions?
Lines to read : when removed from the water and tilted at various angles with the head up, however, blood pressure at their midpoint drops significantly, and at brain level falls to zero.
(B) An organism's reaction to being placed in an environment to which it is not well adapted can sometimes illustrate the problems that have been solved by the adaptations of organisms indigenous to that environment.
---------------------------------------

2. According to the passage, one reason that the distribution of blood in the sea snake changes little while the creature remains in the ocean is that
Lines to read - the vertical pressure gradients within the blood vessels are counteracted by similar pressure gradients in the surrounding water
(B) pressure gradients in the water surrounding the sea snake counter the effects of vertical pressure gradients within its blood vessels
--------------------------------------

3. It can be inferred from the passage that which of the following is true of species of terrestrial snakes that often need to assume a vertical posture?
(B) Their hearts are less likely to be located at the midpoint of their bodies than is the case with sea snakes. --- clearly this is the only choice true.
-------------------------------------

4. The author describes the behavior of the circulatory system of sea snakes when they are removed from the ocean (see lines 17-20) primarily in order to
pre-thinking - The problem confronting terrestrial snakes is best illustrated by what happens to sea snakes when removed from their supportive medium. for giving example on these lines.
(A) illustrate what would occur in the circulatory system of terrestrial snakes without adaptations that enable them to regulate their blood pressure in vertical orientations
-------------------------------------

5. It can be inferred from the passage that which of the following is a true statement about sea snakes?
Confused b/w B and D. B is not given in the passage. we can not make this statement.
(B) They can not effectively regulate their blood pressure when placed in sea water and tilted at an angle with the head pointed downward.
(D) They become acutely vulnerable to the effects of gravitational pressure on their circulatory system when they are placed in a terrestrial environment. - correct.
-------------------------------------

6. The author suggests that which of the following is a disadvantage that results from the location of a snake's heart in close proximity to its head?

(E) An increase in the amount of effort required to distribute blood to and from the snake's tail
-----------------------------------------------

7. The primary purpose of the third paragraph is to
(A) introduce a topic that is not discussed earlier in the passage
(B) describe a more efficient method of achieving an effect discussed in the previous paragraph
(C) draw a conclusion based on information elaborated in the previous paragraph
(D) discuss two specific examples of phenomena mentioned at the end of the previous paragraph -- correct answer. look p3
(E) introduce evidence that undermines a view reported earlier in the passage
-----------------------------------------------

8. In the passage,the author is primarily concerned with doing which of the following?
Clearly A. refer P1 for answer. in p2 and p3, author just gave the example based on p1
(A) Explaining adaptations that enable the terrestrial snake to cope with the effects of gravitational pressure on its circulatory system
(B) Comparing the circulatory system of the sea snake with that of the terrestrial snake
(C) Explaining why the circulatory system of the terrestrial snake is different from that of the sea snake
(D) Pointing out features of the terrestrial snake's cardiovascular system that make it superior to that of the sea snake
(E) Explaining how the sea snake is able to neutralize the effects of gravitational pressure on its circulatory system

I love OG problems, but they seem not as difficult as what I encountered at real GMAT test.
A lot of Manhattan or Veritas prep RCs are much more complicate and tricky than OG's, and seem more close to real GMAT problems, why is that?

This particular thread might not be the best place to ask that question

The OGs are not meant only for test takers who can get (say) 90%+ scores. They therefore have questions across difficulty levels. Also, they are not adaptive, whereas the GMAT is.
_________________

Answer choice analysis is important.
However, more than that, passage understanding to an extent in which one can retain the gist without re-reading the article is SUPREME and highly lucrative.

The passage actually details 2 adaptations:

1) One such adaptation is the closer proximity of the terrestrial snake's heart to its head, which helps to ensure circulation to the brain, regardless of the snake's orientation in space. The heart of sea snakes can be located near the middle of the body, a position that minimizes the work entailed in circulating blood to both extremities. In arboreal snakes, however, which dwell in trees and often assume a vertical posture, the average distance from the heart to the head can be as little as 15 percent of overall body length.

2) Such a location requires that blood circulated to the tail of the snake travel a greater distance back to the heart, a problem solved by another adaptation. When climbing, arboreal snakes often pause momentarily to wiggle their bodies, causing waves of muscle contraction that advance from the lower torso to the head. By compressing the veins and forcing blood forward, these contractions apparently improve the flow of venous blood returning to the heart.

_________________