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Difficulty: 705-805 Level,    Long Passage,    Science,                      
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Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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Passage breakdown


In the first paragraph (P1), the author introduces a debate:

  • There are different hypotheses concerning the development of the vertebrate skeleton.
  • A 1981 discovery regarding conodonts has "important implications" regarding this debate.

In the second paragraph, the author explains both sides of the controversy

  • The traditional view: that the vertebrate skeleton was first developed for defense
  • The other view: that it was developed for predation.
  • The author then provides evidence for each side from BEFORE the 1981 discovery.

In the third paragraph, the author argues that the 1981 discovery supports the "other view"

  • The vertebrate skeleton was developed for predation/aggression, not for defense.

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


Explanations for individual questions


General Discussion
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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Please comment on answer as I have not purchased OG to double check my reasoning.

Tone: Evaluate
Organization:
P1: Describe the significance of a discovery that led to some hypotheses.
P2: Describe 2 hypotheses - traditionalists view and paleontologists view. Authors seems to favor paleotologists' view.

Topic: Discovery of fossils
Scope: Development of vetebrate skeleton based on discovery.

1. D
Uncertain between choice B and D.
B. conodonts' teeth were adapted from protective bony scales
Thus, traditionalists argued, these animals developed coverings of bony scales or plates, and teeth were secondary features, adapted from the protective bony scales.

D. primitive vertebrates with teeth appeared earlier than armored vertebrates
The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms.

Remarks:
Is it always the case that the credited answer is what the author actually intends to support? I finally choose E because the whole passage are gears towards paleontologist view and traditionalists view is just for evaluation, that is, initially it was thought, then (MAIN CONCLUSION).
Furthermore, there is the word indicate which can be concluded as conclude in this case?

2. E present the two sides of the debate concerning the development of the vertebrate skeleton
Uncertain between A and E.
A. It does actually use findings to support each argument.
E. It is mainly about presenting 2 different view using the same evidence?

Remarks:
Chosen E because it encompasses 2 views and is more general.
Usually function question does not include details in the answer.

3. B. Ostracoderms were not the earliest vertebrates.
The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms.

Although I have obtained all credited answer ,but I did not complete in the recommended time.
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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The passage was easy , but the inference for question 1 was tough .
If we read passage carefully we can find the answer to this question, easily.
Reading the following lines reveals that primitive vertebrates with teeth appeared earlier than armored vertebrates
Hence D is the answer.
Teeth were more
primitive than external armor according to this view,
and the earliest vertebrates were predators.
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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how do I find information to answer the first question?

Okay, now I got it.
Lesson: right answers can be found in any paragraph.
A is too extreme because of "actually had been"
E is out because no information found
C is wrong because 1/ too extreme, not all cocodonts 2/ by definition in the first paragraph, concodont is just remains, not animals
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
[quote="anje29"]Official explanation is here

Thanks! Although I feel confused reading this OG explanation about Q1..It mainly talked about P3 when the right answer lies in P2.. [Thus, traditionalists argued, these animals developed coverings of bony scales or plates, and teeth were secondary features, adapted from the protective bony scales. ]

I may have to give up this question because I still can't find any reason to locate that answer in that position...unless you decide to look through all the passage .
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
Hello GMATNinja sayantanc2k

For question 3, although I marked the correct option for Q3, I was confused between B and D. Can you help to explain how to eliminate option D?

It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?
A. The earliest vertebrates were sedentary suspension feeders.
B. Ostracoderms were not the earliest vertebrates.
C. Defensive armor preceded jaws among vertebrates.
D. Paired eyes and adaptations for activity are definitive characteristics of vertebrates.
E. Conodonts were unlikely to have been predators.
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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Hey Dkingdom

The below is para 2 acc to me and hence E is correct

The vertebrate skeleton had traditionally been
regarded as a defensive development, champions of
this view postulating that it was only with the much
later evolution of jaws that vertebrates became
predators. The first vertebrates, which were soft-
(20)
bodied, would have been easy prey for numerous
invertebrate carnivores, especially if these early
vertebrates were sedentary suspension feeders.
Thus, traditionalists argued, these animals developed
coverings of bony scales or plates, and teeth were
(25)
secondary features, adapted from the protective
bony scales. Indeed, external skeletons of this
type are common among the well-known fossils of
ostracoderms, jawless vertebrates that existed from
approximately 500 to 400 million years ago.
(30)
However, other paleontologists argued that many of
the definitive characteristics of vertebrates, such as
paired eyes and muscular and skeletal adaptations
for active life, would not have evolved unless the
(35)
first vertebrates were predatory. Teeth were more
primitive than external armor according to this view,
and the earliest vertebrates were predators.

Hope this helps :-)
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
I have marked initially all correct
D, E, B

But later changed 1) to C
Reason - the answer D is palentologists view
Not the scientists
Since after line 30 was all palentologists arguing comments.

But if we find from line 43 onward what is written is answer D
Confused that it is scientists or palentologists conclusion.

If scientists then in line 19-23 whose idea was that - must be of scientists only. ???
Kindly explain me

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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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There could be a huge debate of where the 2nd passage starts and where it ends. I even looked in official guide 2018 where it can be horridly concluded that the 2nd passage end in line 29.

I just got lost and selected a wrong answer choice. I hope I don't see such instances of bad formatting in actual GMAT.
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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For this one, I think D from this
from (30) However, other paleontologists argued that many of
the definitive characteristics of vertebrates, such as
paired eyes and muscular and skeletal adaptations
for active life, would not have evolved unless the
(35)
first vertebrates were predatory. >> Only here to support that first vertebrate were predatory but does not draw the conclusion of paleontologists. You agree?
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
With reference to question number 1, the passage says, "Thus, traditionalists argued, these animals developed coverings of bony scales or plates, and teeth were secondary features, adapted from the protective bony scales." And by "these animals", the passage clearly refers to "The first vertebrates, which were soft-bodied", which are the conodonts. Thus, we can conclude from the passage that the teeth of the conodont were adapted from protective bony scales.

So, why cant B be the correct option?

Originally posted by aviejay on 14 Mar 2018, 22:51.
Last edited by aviejay on 14 Mar 2018, 23:19, edited 1 time in total.
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
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Hi Abdur,

I really appreciate your effort in posting RCs and other verbal questions but I noticed one thing that you also mentions the line numbers in the RC. GMAT does not do that now in the real exams. So I request you to please do not mention the line numbers as they distract me.

Hope you understand.
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
AbdurRakib wrote:
mbahanoi wrote:
i dont understand this passage
is there any lack of words in line 20?


The missed line added.
Thanks



Could you please confirm when is para 2 ending.
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
TheMechanic wrote:
There could be a huge debate of where the 2nd passage starts and where it ends. I even looked in official guide 2018 where it can be horridly concluded that the 2nd passage end in line 29.

I just got lost and selected a wrong answer choice. I hope I don't see such instances of bad formatting in actual GMAT.



Same thing happened with me. I also thought that the para 2 is ending at line 29 and chose the wrong option on that basis.
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Re: Conodonts, the spiky phosphatic remains (bones and teeth composed of c [#permalink]
GMATNinjaTwo,

Hi GMATNinja, I was wondering could you please explain the difference between option B and E for Q2? I ended up picking option E but it was more of a lucky guess. Would greatly appreciate it if you could please shed some light on option B especially!
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