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## OG Conodonts, the spiky phosphatic remains

This topic has 4 expert replies and 3 member replies
AbeNeedsAnswers Master | Next Rank: 500 Posts
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#### OG Conodonts, the spiky phosphatic remains

Sat Aug 19, 2017 2:07 pm
Conodonts, the spiky phosphatic remains (bones
and teeth composed of calcium phosphate) of
tiny marine animals that probably appeared about
520 million years ago, were once among the most
controversial of fossils. Both the nature of the
organism to which the remains belonged and the
function of the remains were unknown. However,
since the 1981 discovery of fossils preserving not
just the phosphatic elements but also other remains
of the tiny soft-bodied animals (also called conodonts)
that bore them, scientists' reconstructions of the
animals' anatomy have had important implications
for hypotheses concerning the development of the
vertebrate skeleton.

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-
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
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.
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
first vertebrates were predatory. Teeth were more
primitive than external armor according to this view,
and the earliest vertebrates were predators.

The stiffening notochord along the back of the
body, V-shaped muscle blocks along the sides,
and posterior tail fins help to identify conodonts as
among the most primitive of 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. It now appears that the hard parts that
first evolved in the mouth of an animal improved its
efficiency as a predator, and that aggression rather
than protection was the driving force behind the origin
of the vertebrate skeleton.

514) According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that
A. conodonts had actually been invertebrate carnivores
B. conodonts' teeth were adapted from protective bony scales
C. conodonts were primitive vertebrate suspension feeders
D. primitive vertebrates with teeth appeared earlier than armored vertebrates
E. scientists' original observations concerning the phosphatic remains of conodonts were essentially correct

515) The second paragraph in the passage serves primarily to
A. outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton
B. contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains
C. contrast the characteristics of the ostracoderms with the characteristics of earlier soft-bodied vertebrates
D. explain the importance of the development of teeth among the earliest vertebrate predators
E. present the two sides of the debate concerning the development of the vertebrate skeleton

516) 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.

Q514: D
Q515: E
Q516: B

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NandishSS Master | Next Rank: 500 Posts
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Thu Sep 21, 2017 9:23 pm
Hi Dave/Guru/Experts,

Tried my best to map the above passage. Please let me know is this right?

Conodonts-->controversial of fossils--> implications for hypotheses concerning the development of the vertebrate skeleton.

defensive development --> easy prey for numerous invertebrate carnivores-->But Teeth were more
primitive than external armor according to this view, and the earliest vertebrates were predators.

The lack of any mineralized structures --> jawless fishes such as the ostracoderms --> hard parts that first evolved in the mouth --> defense

### Top Member

NandishSS Master | Next Rank: 500 Posts
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344 messages
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Thu Sep 21, 2017 9:30 pm
514) According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that
A. conodonts had actually been invertebrate carnivores
B. conodonts' teeth were adapted from protective bony scales
C. conodonts were primitive vertebrate suspension feeders
D. primitive vertebrates with teeth appeared earlier than armored vertebrates
E. scientists' original observations concerning the phosphatic remains of conodonts were essentially correct

Why is it not C? Where is it mentioned?

515) The second paragraph in the passage serves primarily to
A. outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton
B. contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains
C. contrast the characteristics of the ostracoderms with the characteristics of earlier soft-bodied vertebrates
D. explain the importance of the development of teeth among the earliest vertebrate predators
E. present the two sides of the debate concerning the development of the vertebrate skeleton

Is second paragraph not a comparison or contrast? defensive development -- earliest vertebrates were predators or not?

516) 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.

How to deal with inference question and which are the lines to look back?

bounce87 Junior | Next Rank: 30 Posts
Joined
26 Mar 2016
Posted:
16 messages
Wed Sep 27, 2017 10:18 am
some expert advice on this topic would be helpful!

### GMAT/MBA Expert

DavidG@VeritasPrep Legendary Member
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GMAT Score:
770
Wed Sep 27, 2017 11:10 am
NandishSS wrote:
Hi Dave/Guru/Experts,

Tried my best to map the above passage. Please let me know is this right?

Conodonts-->controversial of fossils--> implications for hypotheses concerning the development of the vertebrate skeleton.

defensive development --> easy prey for numerous invertebrate carnivores-->But Teeth were more
primitive than external armor according to this view, and the earliest vertebrates were predators.

The lack of any mineralized structures --> jawless fishes such as the ostracoderms --> hard parts that first evolved in the mouth --> defense

The gist is of this passage is that there's a debate between two camps regarding the evolution of vertebrates. The traditionalists believe that bony scales (protection) came first. The alternative view is that teeth (predation) came. The new discovery favors the teeth (predation) hypothesis. That's the main thing you want to come away with.

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Save $100 off any live Veritas Prep GMAT Course Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now! ### GMAT/MBA Expert DavidG@VeritasPrep Legendary Member Joined 14 Jan 2015 Posted: 2667 messages Followed by: 120 members Upvotes: 1153 GMAT Score: 770 Wed Sep 27, 2017 11:14 am Quote: 514) According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that A. conodonts had actually been invertebrate carnivores B. conodonts' teeth were adapted from protective bony scales C. conodonts were primitive vertebrate suspension feeders D. primitive vertebrates with teeth appeared earlier than armored vertebrates E. scientists' original observations concerning the phosphatic remains of conodonts were essentially correct In the second paragraph we're first given what the traditionalists believe: Thus, traditionalists argued, these animals developed coverings of bony scales or plates, and teeth were secondary features In other words, scales or plates came before teeth. The discovery of the conodonts undermined the traditionalist belief. Note the last line of the passage: It now appears that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton. So teeth came first. The answer is D _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

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### GMAT/MBA Expert

DavidG@VeritasPrep Legendary Member
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Wed Sep 27, 2017 11:16 am
Quote:
515) The second paragraph in the passage serves primarily to
A. outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton
B. contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains
C. contrast the characteristics of the ostracoderms with the characteristics of earlier soft-bodied vertebrates
D. explain the importance of the development of teeth among the earliest vertebrate predators
E. present the two sides of the debate concerning the development of the vertebrate skeleton
The second paragraph first gives us the traditional belief. The structural clue that we're going to get a competing belief is the transition, "however." However, other paleontologists argued

So we're getting two sides of an argument. The answer is E

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Save $100 off any live Veritas Prep GMAT Course Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now! ### GMAT/MBA Expert DavidG@VeritasPrep Legendary Member Joined 14 Jan 2015 Posted: 2667 messages Followed by: 120 members Upvotes: 1153 GMAT Score: 770 Wed Sep 27, 2017 11:19 am Quote: 516) 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. The key is this sentence in the third paragraph: 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. If the conodonts were primitive than the ostracoderms, then the conodonts came first. Thus, the ostracoderms could not have been the earliest vertebrates. The answer is B _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

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