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Flatfish, such as the flounder, are among the few vertebrates that lac

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Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New Project RC Butler 2019 - Practice 2 RC Passages Everyday
Passage # 79, Date : 12-MAR-2019
This post is a part of New Project RC Butler 2019. Click here for Details


Flatfish, such as the flounder, are among the few vertebrates that lack approximate bilateral symmetry (symmetry in which structures to the left and right of the body's midline are mirror images). Most striking among the many asymmetries evident in an adult flatfish is eye' placement: before maturity one eye migrates, so that in an adult flatfish both eyes are on the same side of the head. While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed. In the waters between the United States and Japan, the starry flounder populations vary from about 50 percent left-eyed off the United States West Coast, through about 70 percent left eyed halfway between the United States and Japan, to nearly 100 percent left-eyed off the Japanese coast.

Biologists call this kind of gradual variation over·a certain geographic range a "cline" and interpret dines as strong indications that the variation is adaptive, a response to environmental differences. For the starry flounder this interpretation implies that a geometric difference (between fish that are mirror images of one another) is adaptive, that left-eyedness in the Japanese starry flounder has been selected for, which provokes a perplexing question: what is the selective advantage in having both eyes on one side rather than on the other?

The ease with which a fish can reverse the effect of the sidedness of its eye asymmetry simply by turning around has caused biologists to study internal anatomy, especially the optic nerves, for the answer. In all flatfish, the optic nerves cross, so that the right optic nerve is joined to the brain's left side and vice versa. This crossing introduces an asymmetry, as one optic nerve must cross above or below the other. G. H. Parker reasoned that if, for example, a flatfish's left eye migrated when the right optic nerve was on top, there would be a twisting of nerves, which might be mechanically disadvantageous. For starry flounders, then, the left-eyed variety would be selected against, since in a starry flounder the left optic nerve is uppermost.

The problem with the above explanation is that the Japanese starry flounder population is almost exclusively left-eyed, and natural selection never promotes a purely less advantageous variation. As other explanations proved equally untenable, biologists concluded that there is no important adaptive difference between left-eyedness and right-eyedness and that the two characteristics are genetically associated with some other adaptively significant characteristic. This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral. As for the left-eyed and right-eyed flatfish, their difference, however striking, appears to be an evolutionary red herring.

Spoiler: :: OA
C

1. According to the passage, starry flounder differ from most other species of flatfish in that starry flounder

(A) are not basically bilaterally symmetric
(B) do not become asymmetric until adulthood
(C) do not all share the same asymmetry
(D) have both eyes on the same side of the head
(E) tend to cluster in only certain geographic regions


Spoiler: :: OA
D

2. The author would be most likely to agree with which of the following statements about left-eyedness and right-eyedness in the starry flounder?

I. They are adaptive variations by the starry flounder to environmental differences.
II. They do not seem to give obvious selective advantages to the starry flounder.
III. They occur in different proportions in different locations.

(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III


Spoiler: :: OA
E

3. According to the passage, a possible disadvantage associated with eye migration in flatfish is that the optic nerves can

(A) adhere to one another
(B) detach from the eyes
(C) cross
(D) stretch
(E) twist


Spoiler: :: OA
A

4. Which of the following best describes the organization of the passage as a whole?

(A) A phenomenon is described and an interpretation presented and rejected.
(B) A generalization is made and supporting evidence is supplied and weighed.
(C) A contradiction is noted and a resolution is suggested and then modified.
(D) A series of observations is presented and explained in terms of the dominant theory.
(E) A hypothesis is introduced and corroborated in the light of new evidence.


Spoiler: :: OA
B

5. The passage supplies information for answering which of the following questions?

(A) Why are Japanese starry flounder mostly left-eyed?
(B) Why should the eye-sidedness in starry flounder be considered selectively neutral?
(C) Why have biologists recently become interested in whether a characteristic is adaptive or selectively neutral?
(D) How do the eyes in flatfish migrate?
(E) How did Parker make his discoveries about the anatomy of optic nerves in flatfish?


Spoiler: :: OA
D

6. Which of the following is most clearly similar to a cline as it is described in the second paragraph of the passage?

(A) A vegetable market in which the various items are grouped according to place of origin
(B) A wheat field in which different varieties of wheat are planted to yield a crop that will bring the maximum profit
(C) A flower stall in which the various species of flowers are arranged according to their price
(D) A housing development in which the length of the front struts supporting the porch of each house increases as houses are built up the hill
(E) A national park in which the ranger stations are placed so as to be inconspicuous, and yet as easily accessible as possible


Spoiler: :: OA
E

7. Which of the following phrases from the passage best expresses the author's conclusion about the meaning of the difference between left -eyed and right-eyed flatfish?

(A) "Most striking"
(B) "variation is adaptive"
(C) "mechanically disadvantageous"
(D) "adaptively significant"
(E) "evolutionary red herring"



Source: GRE Official Material
Difficulty Level: 700

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Originally posted by carcass on 09 Mar 2019, 10:35.
Last edited by SajjadAhmad on 27 Mar 2020, 08:51, edited 3 times in total.
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 13 Mar 2019, 10:37
5
This was a relatively difficult passage. I spent at least 4mins reading the passage and summarising each paragraph mentally (as well as noting a few points). Total time spent: 14.5 mins with the last 2 questions being fairly rushed with zero workings. I got 4 (due to picking the wrong answer I did not mean to pick) and 5 wrong. 5-6/7. That's okay. I tend to set up A B C D E (religiously) in the top right hand corner of my workbook/sheet and from there write a circle beneath the letter which may have the right answer, x which appears to be definitely wrong and a tick for the right answer (though this is a waste of time on the exam and you can just quickly select the right answer on your screen).

Question 1: This tests eye for detail and whilst the answers are tricky you can cross out the ones that are wrong such as A and E (and B if you spotted that). Asymmetry does not equate to the positioning of the object (and earlier in high school you may have gotten that wrong) and so it is important to question the specific language used here. Semantics, Gods of Language, rule supreme on Verbal generally.


Question 2: Almost more than one question in one but if you started with III(which appears the most in the answer choices) then you would be able to immediately cross out A and B. The answers are kind of spread out throughout the passage but with II this is where your understanding of the passage becomes very handy and you know it is correct. I is wrong since although this is reference to "environmental" differences this is not applied to our subject, the flounder and so must be rejected. We are left with II and III (correct as you will find in the statistics of the first paragraph).

Question 3: I think reference is made to some of the other verbs but the question ask specifically for the "disadvantages"

Question 4: I think you would have narrowed it down to A and B. Hopefully you would have had some inclination as to structure from the first read (as well as a review of paragraphs where necessary). See my reasoning to Q7 below. To understand that the answer is A you would need to understand the conclusion that the authors provides: that the adaptive characteristic is a logical fallacy i.e. a "red-herring"

Question 5: This is the question I got wrong and anyone reading this should still note that my logic is shaky. At first I selected D on the basis of the following part in the passage: 'flatfish's left eye migrated when the right optic nerve was on top, there would be a twisting of nerves'. No reason however is given as to the 'why'. The actual answer B relates to the final paragraph where there is a reference to 'selectively neutral' but the logical argument only comes prior to the actual reference and so it is easy to miss the trick. If you read the paragraph in full (until the reference) you can see that the author does indeed question.

Question 6: These are probably the toughest questions. Emphasis throughout the passage is on the adaptive (and presumably defensive nature) of the symmetry and placement of the eyes and so if you narrowed it down to B and D then the answer may have been obvious. Hopefully you would not have pondered E too much (as I guess it does not make the defensive/adaptive characteristic too obvious).

Question 7: the key is understanding the meaning of the phrase "red-herring" right at the end of the passage. If you read opinion columns, then you may have come across this. Luckily (emphasis on 'luck') I have and knew what this meant. General reading does indeed help.
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 02 Jul 2019, 13:26
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Honestly, this was really tough. Wow. If it was not 800 level it was close, really close.

Thinking during the exam pressure to grasp this passage was surely difficult. I think I needed the five gear :|

Anyhow, after reading it twice I came up that these are clearly wrong.

(D) How do the eyes in flatfish migrate?
(E) How did Parker make his discoveries about the anatomy of optic nerves in flatfish?

Move one

This

(A) Why are Japanese starry flounder mostly left-eyed?

We do know this from the first paragraph is adaptive, that left-eyedness in the Japanese starry flounder has been selected for, . The question is almost an inference from all over the passage. The answer could be anywhere , even in a tiny sentence or a prepositional phrase.

(B) Why should the eye-sidedness in starry flounder be considered selectively neutral?
(C) Why have biologists recently become interested in whether a characteristic is adaptive or selectively neutral?

C is wrong for the following

This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral.

Which means that the question the biologist wonder, basically does not exists. Because they already know. So C is redundant.

B is the answer

As other explanations proved equally untenable, biologists concluded that there is no important adaptive difference between left-eyedness and right-eyedness and that the two characteristics are genetically associated with some other adaptively significant characteristic..

Which means that the fish being neutral is not the only reason. Something else must come in play.

:death:

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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 27 Apr 2020, 23:48
2
Hi everyone,
Got 5/7 correct in 12.30 minutes, including 5 minutes to read and 7:30 minutes to answer the questions.

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


P1

In paragraph one we are given that the flatfish has a special kind of asymmetry: usually this fish has both eyes either on the right or left side.
Then we are given the distributions of right eyed and left eyed flatfishes between the US and Japan: surprisingly the flatfishes close to Japan are all left eyed.

Purpose: to present the asymmetry typical of the flatfish and the distributions of such fish between US and Japan




P2

In this paragraph the author introduces the point of view of biologists. They think that the asymmetry of the flatfish is adaptive. The the author asks why having both eyes on the right or on the left should result from an environmental condition, that is what is the advantage?

Purpose: to present the biologists' point of view, that is flatfish's asymmetry is adaptive




P3

In paragraph 3 the author dives into the anatomy of the asymmetry. According to such studies having 2 eyes on the left or right side of the head would be disadvantageous form a mechanical point of view.

Purpose: to claim that the asymmetry is disadvantageous.



P4

Here the author refutes the adaptive theory and class that there is no advantage for the flatfish in having both eyes on the right or left side of the head. Lastly the author presents the point of view of evolutionary biologists, according to whom the cause of the asymmetry is an evolutionary red herring.

Purpose: To refute the adaptive theory and to suggest another explanation for the asymmetry



Main point

To try to provide an explanation for the asymmetry of the flatfish, evaluating a theory and refuting it in favor of another.



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



1. According to the passage, starry flounder differ from most other species of flatfish in that starry flounder

Pre-thinking

Detail question

From P1:
    members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed.



(A) are not basically bilaterally symmetric
(B) do not become asymmetric until adulthood
(C) do not all share the same asymmetry
(D) have both eyes on the same side of the head
(E) tend to cluster in only certain geographic regions




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


2. The author would be most likely to agree with which of the following statements about left-eyedness and right-eyedness in the starry flounder?

Pre-thinking

Inference question

Let's evaluate the options


I. They are adaptive variations by the starry flounder to environmental differences.
the author disputes this theory in the last two paragraphs. See paragraphs summaries above.

II. They do not seem to give obvious selective advantages to the starry flounder.
Yes, as claimed in P3 by G. H. Parker

III. They occur in different proportions in different locations.
Correct. We can infer this option from the last sentences of P1.

(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III



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


3. According to the passage, a possible disadvantage associated with eye migration in flatfish is that the optic nerves can

Pre-thinking

Detail question

From P3:
    there would be a twisting of nerves, which might be mechanically disadvantageous.



(A) adhere to one another
(B) detach from the eyes
(C) cross
(D) stretch
(E) twist



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



4. Which of the following best describes the organization of the passage as a whole?

Pre-thinking

Structure question

Introduction of the topic: bilateral asymmetry in Flounders------> proposal of a theory: Adaptability------> refutation of the theory-------> proposal of another explanation


(A) A phenomenon is described and an interpretation presented and rejected.
(B) A generalization is made and supporting evidence is supplied and weighed.
(C) A contradiction is noted and a resolution is suggested and then modified.
(D) A series of observations is presented and explained in terms of the dominant theory.
(E) A hypothesis is introduced and corroborated in the light of new evidence.



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



5. The passage supplies information for answering which of the following questions?

Pre-thinking

Detail question

Let's evaluate the options


(A) Why are Japanese starry flounder mostly left-eyed?
Never mentioned in the passage.

(B) Why should the eye-sidedness in starry flounder be considered selectively neutral?
From P4:
    This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral. As for the left-eyed and right-eyed flatfish, their difference, however striking, appears to be an evolutionary red herring.

It is clear that such biologists have to make a choice. They refuted the adaptive option so it has to be the other. Later we are given the why aspect, that is an evolutionary red herring.


(C) Why have biologists recently become interested in whether a characteristic is adaptive or selectively neutral?
Never mentioned

(D) How do the eyes in flatfish migrate?
[b]carcass can you explain why this option is wrong? in P3 we are given how the nerves have to move so... isn't it the how aspect of the eyes' shift?[/b]

(E) How did Parker make his discoveries about the anatomy of optic nerves in flatfish?
Never mentioned



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


. Which of the following is most clearly similar to a cline as it is described in the second paragraph of the passage?

Pre-thinking

Analogous statement question

We need to find a variation caused by environmental factors.


(A) A vegetable market in which the various items are grouped according to place of origin
(B) A wheat field in which different varieties of wheat are planted to yield a crop that will bring the maximum profit
(C) A flower stall in which the various species of flowers are arranged according to their price
(D) A housing development in which the length of the front struts supporting the porch of each house increases as houses are built up the hill
(E) A national park in which the ranger stations are placed so as to be inconspicuous, and yet as easily accessible as possible




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



7. Which of the following phrases from the passage best expresses the author's conclusion about the meaning of the difference between left -eyed and right-eyed flatfish?

Pre-thinking

Detail question

From last paragraph:
    As for the left-eyed and right-eyed flatfish, their difference, however striking, appears to be an evolutionary red herring.



(A) "Most striking"
(B) "variation is adaptive"
(C) "mechanically disadvantageous"
(D) "adaptively significant"
(E) "evolutionary red herring"




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

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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 27 Mar 2020, 12:12
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Sajal089 wrote:
q1 and q5 explaination pls


1. According to the passage, starry flounder differ from most other species of flatfish in that starry flounder

On this topic, the passage states, "While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed." In other words, in other species, asymmetries are the same across all individual adults, whereas the starry flounder adults can have different asymmetries.

(A) are not basically bilaterally symmetric All flatfish are asymmetric as per the first sentence of the passage. Eliminate.

(B) do not become asymmetric until adulthood Flatfish (including, presumably, the starry flounder) become asymmetric before maturity ("...before maturity one eye migrates..."). Eliminate.

(C) do not all share the same asymmetry Correct. Consistent with our thinking above.

(D) have both eyes on the same side of the head This is true of all flatfish. Eliminate.

(E) tend to cluster in only certain geographic regions No such information in the passage. Eliminate.

5. The passage supplies information for answering which of the following questions?

(A) Why are Japanese starry flounder mostly left-eyed? This information is not given in the passage. The passage states "As other explanations proved equally untenable, biologists concluded that there is no important adaptive difference between left-eyedness and right-eyedness". Eliminate.

(B) Why should the eye-sidedness in starry flounder be considered selectively neutral? This is explained by the same sentence as mentioned for (A). Correct.Answer.

(C) Why have biologists recently become interested in whether a characteristic is adaptive or selectively neutral? This information is not given in the passage. Eliminate.

(D) How do the eyes in flatfish migrate? This information is not given in the passage - we do not know exactly how the eyes migrate. Eliminate.

(E) How did Parker make his discoveries about the anatomy of optic nerves in flatfish? This information is not given in the passage - we do not know exactly how he made his discoveries. Eliminate.

Hope this helps.
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 16 May 2020, 19:39
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Took me 11 mins to get 6 out of 7 correct. For question 5 I'm still don't understand why my selection is wrong, would appreciate if anyone can shed some light on.

Reading Note

Paragraph 1: Introduce the term of bilateral symmetry. Flat fish lack it, but most species should share the same asymmetry. However starry flounder don't. Some examples of different proportion at different location.

Paragraph 2: Biologist call it "dine" (or cline? probably a typo here), and think it's adaptive. But question raised regarding what pros it gave starry flounder

Paragraph 3: experiment conducted and mechanism of optic nerve crossing introduced. GH Parker reasoned which side of optic nerve comes on top, it would be selected against. In the case it would be left side not favored

Paragraph 4: however most Japan sf is left eyed. so it shouldn't be naturally selected. no specific reason found, probably "evolutionary red herring"

Question

1. According to the passage, starry flounder differ from most other species of flatfish in that starry flounder

(A) are not basically bilaterally symmetric
(B) do not become asymmetric until adulthood
(C) do not all share the same asymmetry
(D) have both eyes on the same side of the head
(E) tend to cluster in only certain geographic regions

You can find the answer in the first passage "While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed.", so C is the right answer

2. The author would be most likely to agree with which of the following statements about left-eyedness and right-eyedness in the starry flounder?

I. They are adaptive variations by the starry flounder to environmental differences.
II. They do not seem to give obvious selective advantages to the starry flounder.
III. They occur in different proportions in different locations.

(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III

The last paragraph clearly puts "environmental differences" in question, so I is out.
II coincides with "As other explanations proved equally untenable, biologists concluded that there is no important adaptive difference between left-eyedness and right-eyedness and that the two characteristics are genetically associated with some other adaptively significant characteristic.", keep it
III can be proved with last few sentences in paragraph 1. So answer D is correct


3. According to the passage, a possible disadvantage associated with eye migration in flatfish is that the optic nerves can

(A) adhere to one another
(B) detach from the eyes
(C) cross
(D) stretch
(E) twist

refer to "G. H. Parker reasoned that if, for example, a flatfish's left eye migrated when the right optic nerve was on top, there would be a twisting of nerves, which might be mechanically disadvantageous." in paragraph 2, the answer is E


4. Which of the following best describes the organization of the passage as a whole?

(A) A phenomenon is described and an interpretation presented and rejected.
(B) A generalization is made and supporting evidence is supplied and weighed.
(C) A contradiction is noted and a resolution is suggested and then modified.
(D) A series of observations is presented and explained in terms of the dominant theory.
(E) A hypothesis is introduced and corroborated in the light of new evidence.

The entire paragraph starts with unusual phenomenon, then the 2nd paragraph provides one explanation but with some questions remained, the 3rd develops further with GH Parker's finding, but got contradicted by examples of Japanese sf. The conclusion is that the unusual asymmetry is not a adaption but evolutionary red herring, which means it's not important.

So B, D, E are out because they still think the original "selection" theory is supported
Then between A and C, C mentioned "a resolution is suggested" but the passage didn't introduce any resolution (decision) other than possible explanations. So the correct answer is A


5. The passage supplies information for answering which of the following questions?

(A) Why are Japanese starry flounder mostly left-eyed?
(B) Why should the eye-sidedness in starry flounder be considered selectively neutral?
(C) Why have biologists recently become interested in whether a characteristic is adaptive or selectively neutral?
(D) How do the eyes in flatfish migrate?
(E) How did Parker make his discoveries about the anatomy of optic nerves in flatfish?


The entire passage is trying to figure out why Japanese sf is mostly left-eyed but didn't come up with any solid explanation, so A is out.
"why biologists are interested" is out of scope - C is out
"how did Parker makes the discoveries' is out of scope, E is out
D - I think "In all flatfish, the optic nerves cross, so that the right optic nerve is joined to the brain's left side and vice versa." perfectly explain how do the eyes migrate, what other kinds of info are needed to make a full explanation?



6. Which of the following is most clearly similar to a cline as it is described in the second paragraph of the passage?

(A) A vegetable market in which the various items are grouped according to place of origin
(B) A wheat field in which different varieties of wheat are planted to yield a crop that will bring the maximum profit
(C) A flower stall in which the various species of flowers are arranged according to their price
(D) A housing development in which the length of the front struts supporting the porch of each house increases as houses are built up the hill
(E) A national park in which the ranger stations are placed so as to be inconspicuous, and yet as easily accessible as possible

the "cline" refers to "gradual variation over a certain geographic range". So the correct answer should contain 3 elements - "gradual variation", "geographic range/change" and a hiden one "same species"
A) I don't think this contain either one of the elements, out
B) "different varieties" <> "variation geographically", unless the varieties changed in different locations
C) same flaw as B, out
D) BINGO, we have "increasing length of front struts" and "up the hill", Correct answer
E) same flaw as B and C, out


7. Which of the following phrases from the passage best expresses the author's conclusion about the meaning of the difference between left -eyed and right-eyed flatfish?

(A) "Most striking"
(B) "variation is adaptive"
(C) "mechanically disadvantageous"
(D) "adaptively significant"
(E) "evolutionary red herring"

Pretty straightforward question, refer to the last sentence. Correct answer is E.
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 25 May 2020, 07:09
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livfcind wrote:
PhantomAY wrote:
livfcind wrote:
PhantomAY wrote:
livfcind wrote:
For Q6, the passage you have quoted - hasn't that theory been rejected? So actually it is still unanswered?


Good question - the rejection is on the fact that flatfish's eye placement is not a result of response to environmental differences (the cause), not on the term "cline" itself which ONLY describes the phenomenon - "gradual variation over a certain geographic range".


I'm sorry, I meant Q5, for which you still don't get why B is incorrect.


I assume you mean D? B is correct for "This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral.", given "adaptive" is rejected "selectively neutral" is the only cause.

For D) How do the eyes in flatfish migrate?, I assume it ask for the mechanism behind eye migration (like how you fix your car, not "why you have to fix your car"). The cause "being adaptive" (why you have to fix car) was rejected for sure, but the info presented still explains the mechanism of eye migration - optic nerve crossing (how you fix your car). Does that make sense to you?


But if the 'optic nerve crossing' part is true -> it would also mean that it leads to twisting of nerves -> mechanically disadvantageous.
However, we know that that is not true. Hence I don't think option D has been answered in the passage.
That's how i ruled out D.


I appreciate the discussion here livfcind! :)

"In all flatfish, the optic nerves cross, so that the right optic nerve is joined to the brain's left side and vice versa. This crossing introduces an asymmetry, as one optic nerve must cross above or below the other. G. H. Parker reasoned that if, for example, a flatfish's left eye migrated when the right optic nerve was on top, there would be a twisting of nerves, which might be mechanically disadvantageous. For starry flounders, then, the left-eyed variety would be selected against, since in a starry flounder the left optic nerve is uppermost."

To my understanding, above highlighted in BLUE session is given as facts while the red session is Parker's interpretation of the blue session. He argued that because the right optic nerve was on the top, eye migration should favor the right. This understanding has been rejected by last Paragraph by citing the Japanese case. But it didn't attack the premise (optic nerve crossing) but the conclusion of Parker reasoning it should favor right eye migration.

The mechanism should be the same, the differences are just how people interpret it. Or maybe I'm reading too much into it...
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 02 Jul 2019, 09:17
carcass redskull @crackverbal mikemcgarry Skywalker18

Can you explain question#5.

I got this wrong and cannot figure out still.
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 27 Mar 2020, 00:53
q1 and q5 explaination pls
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 23 May 2020, 11:04
PhantomAY wrote:
Took me 11 mins to get 6 out of 7 correct. For question 5 I'm still don't understand why my selection is wrong, would appreciate if anyone can shed some light on.

Reading Note

Paragraph 1: Introduce the term of bilateral symmetry. Flat fish lack it, but most species should share the same asymmetry. However starry flounder don't. Some examples of different proportion at different location.

Paragraph 2: Biologist call it "dine" (or cline? probably a typo here), and think it's adaptive. But question raised regarding what pros it gave starry flounder

Paragraph 3: experiment conducted and mechanism of optic nerve crossing introduced. GH Parker reasoned which side of optic nerve comes on top, it would be selected against. In the case it would be left side not favored

Paragraph 4: however most Japan sf is left eyed. so it shouldn't be naturally selected. no specific reason found, probably "evolutionary red herring"

Question

1. According to the passage, starry flounder differ from most other species of flatfish in that starry flounder

(A) are not basically bilaterally symmetric
(B) do not become asymmetric until adulthood
(C) do not all share the same asymmetry
(D) have both eyes on the same side of the head
(E) tend to cluster in only certain geographic regions

You can find the answer in the first passage "While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed.", so C is the right answer

2. The author would be most likely to agree with which of the following statements about left-eyedness and right-eyedness in the starry flounder?

I. They are adaptive variations by the starry flounder to environmental differences.
II. They do not seem to give obvious selective advantages to the starry flounder.
III. They occur in different proportions in different locations.

(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III

The last paragraph clearly puts "environmental differences" in question, so I is out.
II coincides with "As other explanations proved equally untenable, biologists concluded that there is no important adaptive difference between left-eyedness and right-eyedness and that the two characteristics are genetically associated with some other adaptively significant characteristic.", keep it
III can be proved with last few sentences in paragraph 1. So answer D is correct


3. According to the passage, a possible disadvantage associated with eye migration in flatfish is that the optic nerves can

(A) adhere to one another
(B) detach from the eyes
(C) cross
(D) stretch
(E) twist

refer to "G. H. Parker reasoned that if, for example, a flatfish's left eye migrated when the right optic nerve was on top, there would be a twisting of nerves, which might be mechanically disadvantageous." in paragraph 2, the answer is E


4. Which of the following best describes the organization of the passage as a whole?

(A) A phenomenon is described and an interpretation presented and rejected.
(B) A generalization is made and supporting evidence is supplied and weighed.
(C) A contradiction is noted and a resolution is suggested and then modified.
(D) A series of observations is presented and explained in terms of the dominant theory.
(E) A hypothesis is introduced and corroborated in the light of new evidence.

The entire paragraph starts with unusual phenomenon, then the 2nd paragraph provides one explanation but with some questions remained, the 3rd develops further with GH Parker's finding, but got contradicted by examples of Japanese sf. The conclusion is that the unusual asymmetry is not a adaption but evolutionary red herring, which means it's not important.

So B, D, E are out because they still think the original "selection" theory is supported
Then between A and C, C mentioned "a resolution is suggested" but the passage didn't introduce any resolution (decision) other than possible explanations. So the correct answer is A


5. The passage supplies information for answering which of the following questions?

(A) Why are Japanese starry flounder mostly left-eyed?
(B) Why should the eye-sidedness in starry flounder be considered selectively neutral?
(C) Why have biologists recently become interested in whether a characteristic is adaptive or selectively neutral?
(D) How do the eyes in flatfish migrate?
(E) How did Parker make his discoveries about the anatomy of optic nerves in flatfish?


The entire passage is trying to figure out why Japanese sf is mostly left-eyed but didn't come up with any solid explanation, so A is out.
"why biologists are interested" is out of scope - C is out
"how did Parker makes the discoveries' is out of scope, E is out
D - I think "In all flatfish, the optic nerves cross, so that the right optic nerve is joined to the brain's left side and vice versa." perfectly explain how do the eyes migrate, what other kinds of info are needed to make a full explanation?



6. Which of the following is most clearly similar to a cline as it is described in the second paragraph of the passage?

(A) A vegetable market in which the various items are grouped according to place of origin
(B) A wheat field in which different varieties of wheat are planted to yield a crop that will bring the maximum profit
(C) A flower stall in which the various species of flowers are arranged according to their price
(D) A housing development in which the length of the front struts supporting the porch of each house increases as houses are built up the hill
(E) A national park in which the ranger stations are placed so as to be inconspicuous, and yet as easily accessible as possible

the "cline" refers to "gradual variation over a certain geographic range". So the correct answer should contain 3 elements - "gradual variation", "geographic range/change" and a hiden one "same species"
A) I don't think this contain either one of the elements, out
B) "different varieties" <> "variation geographically", unless the varieties changed in different locations
C) same flaw as B, out
D) BINGO, we have "increasing length of front struts" and "up the hill", Correct answer
E) same flaw as B and C, out


7. Which of the following phrases from the passage best expresses the author's conclusion about the meaning of the difference between left -eyed and right-eyed flatfish?

(A) "Most striking"
(B) "variation is adaptive"
(C) "mechanically disadvantageous"
(D) "adaptively significant"
(E) "evolutionary red herring"

Pretty straightforward question, refer to the last sentence. Correct answer is E.


For Q6, the passage you have quoted - hasn't that theory been rejected? So actually it is still unanswered?
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 23 May 2020, 13:15
livfcind wrote:
PhantomAY wrote:
Took me 11 mins to get 6 out of 7 correct. For question 5 I'm still don't understand why my selection is wrong, would appreciate if anyone can shed some light on.

....


For Q6, the passage you have quoted - hasn't that theory been rejected? So actually it is still unanswered?


Good question - the rejection is on the fact that flatfish's eye placement is not a result of response to environmental differences (the cause), not on the term "cline" itself which ONLY describes the phenomenon - "gradual variation over a certain geographic range".
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New post 24 May 2020, 00:21
PhantomAY wrote:
livfcind wrote:
PhantomAY wrote:
Took me 11 mins to get 6 out of 7 correct. For question 5 I'm still don't understand why my selection is wrong, would appreciate if anyone can shed some light on.

....


For Q6, the passage you have quoted - hasn't that theory been rejected? So actually it is still unanswered?


Good question - the rejection is on the fact that flatfish's eye placement is not a result of response to environmental differences (the cause), not on the term "cline" itself which ONLY describes the phenomenon - "gradual variation over a certain geographic range".


I'm sorry, I meant Q5, for which you still don't get why B is incorrect.
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 24 May 2020, 12:29
livfcind wrote:
PhantomAY wrote:
livfcind wrote:
PhantomAY wrote:
Took me 11 mins to get 6 out of 7 correct. For question 5 I'm still don't understand why my selection is wrong, would appreciate if anyone can shed some light on.

....


For Q6, the passage you have quoted - hasn't that theory been rejected? So actually it is still unanswered?


Good question - the rejection is on the fact that flatfish's eye placement is not a result of response to environmental differences (the cause), not on the term "cline" itself which ONLY describes the phenomenon - "gradual variation over a certain geographic range".


I'm sorry, I meant Q5, for which you still don't get why B is incorrect.


I assume you mean D? B is correct for "This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral.", given "adaptive" is rejected "selectively neutral" is the only cause.

For D) How do the eyes in flatfish migrate?, I assume it ask for the mechanism behind eye migration (like how you fix your car, not "why you have to fix your car"). The cause "being adaptive" (why you have to fix car) was rejected for sure, but the info presented still explains the mechanism of eye migration - optic nerve crossing (how you fix your car). Does that make sense to you?
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac  [#permalink]

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New post 24 May 2020, 22:02
PhantomAY wrote:
livfcind wrote:
PhantomAY wrote:
livfcind wrote:
PhantomAY wrote:
Took me 11 mins to get 6 out of 7 correct. For question 5 I'm still don't understand why my selection is wrong, would appreciate if anyone can shed some light on.

....


For Q6, the passage you have quoted - hasn't that theory been rejected? So actually it is still unanswered?


Good question - the rejection is on the fact that flatfish's eye placement is not a result of response to environmental differences (the cause), not on the term "cline" itself which ONLY describes the phenomenon - "gradual variation over a certain geographic range".


I'm sorry, I meant Q5, for which you still don't get why B is incorrect.


I assume you mean D? B is correct for "This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral.", given "adaptive" is rejected "selectively neutral" is the only cause.

For D) How do the eyes in flatfish migrate?, I assume it ask for the mechanism behind eye migration (like how you fix your car, not "why you have to fix your car"). The cause "being adaptive" (why you have to fix car) was rejected for sure, but the info presented still explains the mechanism of eye migration - optic nerve crossing (how you fix your car). Does that make sense to you?


But if the 'optic nerve crossing' part is true -> it would also mean that it leads to twisting of nerves -> mechanically disadvantageous.
However, we know that that is not true. Hence I don't think option D has been answered in the passage.
That's how i ruled out D.
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Re: Flatfish, such as the flounder, are among the few vertebrates that lac   [#permalink] 24 May 2020, 22:02

Flatfish, such as the flounder, are among the few vertebrates that lac

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