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evolution takes place

by arora007 » Wed Jul 14, 2010 11:40 am
source: McGraw Hill's Conquering GMAT Verbal and writing

Most biologists agree that evolution takes place extremely
slowly, with species requiring millions and millions of years
to accumulate enough small changes to gradually transform
into new ones. For the �rst 4 billion years of Earth's his-
tory, the only species known were bacteria, plankton, and
algae. But the fossil record indicates that during a brief
30 million year span known as the Cambrian explosion, the
eventual lineages of all major animal groups alive today
appeared.
Which of the following, if true, provides at least a partial
explanation for the discrepancy outlined above?
A. The fossil record only represents a small portion of the species
alive at any given time.
B. The fossil record indicates a number of major extinction events
in Earth's history.
C. Some of the lineages found in the fossil record of the Cambrian
explosion are no longer alive today.
D. Bacteria, plankton, and algae leave little evidence in the fossil
record because of their physical structures.
E. The fossil record indicates a large diversity in the plant species
inhabiting the Earth during the Cambrian explosion.

If you choose a choice please explain why.

OA-A
Last edited by arora007 on Thu Jul 15, 2010 2:45 am, edited 1 time in total.
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by diebeatsthegmat » Thu Jul 15, 2010 12:43 am
arora007 wrote:source: McGraw Hill's Conquering GMAT Verbal and writing

Most biologists agree that evolution takes place extremely
slowly, with species requiring millions and millions of years
to accumulate enough small changes to gradually transform
into new ones. For the �rst 4 billion years of Earth's his-
tory, the only species known were bacteria, plankton, and
algae. But the fossil record indicates that during a brief
30 million year span known as the Cambrian explosion, the
eventual lineages of all major animal groups alive today
appeared.
Which of the following, if true, provides at least a partial
explanation for the discrepancy outlined above?
A. The fossil record only represents a small portion of the species
alive at any given time.
B. The fossil record indicates a number of major extinction events
in Earth's history.
C. Some of the lineages found in the fossil record of the Cambrian
explosion are no longer alive today.
D. Bacteria, plankton, and algae leave little evidence in the fossil
record because of their physical structures.
E. The fossil record indicates a large diversity in the plant species
inhabiting the Earth during the Cambrian explosion.

If you choose a choice please explain why.
my option is D because D can explain the diffirent time between 4 billion years and 30 billion years in the fossil.
what is the answer?
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by Shawshank » Thu Jul 15, 2010 12:53 am
IMO -- B

The if only algae, bacteria survived, thne the presence of other species should be negated by their extinction..
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by paes » Thu Jul 15, 2010 8:51 am
IMO D

no clue how A is OA.
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by hero » Thu Jul 15, 2010 12:51 pm
Is the question asking to explain why the discrepancy exists in the statement or is it asking to basically fill in the gaps of the discrepancy?

i guess what i'm asking is what type of question is this?
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by debmalya_dutta » Thu Jul 15, 2010 8:19 pm
SAME HERE...i thought the answer was D.

My understanding is that the discrepancy is between
Most biologists agree that evolution takes place extremely slowly, with species requiring millions and millions of years

But the fossil record indicates that during a brief 30 million year span known as the Cambrian explosion, the eventual lineages of all major animal groups alive today appeared.

So do you guys agree that this is the discrepancy ?
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by sk818020 » Thu Jul 15, 2010 8:29 pm
I agree I think this is a poorly written question.

A. says that the fossil record only represents a small portion of the species alive at a given time. From the passage;

"But the fossil record indicates that during a brief
30 million year span known as the Cambrian explosion, the
eventual lineages of all major animal groups alive today
appeared. "

From this you can conclude that the fossil records indicate that there was dramatically more species relative to the periods of time before the date of these fossils. (A) says that there were actually more species than what fossils indicate. This point is irrelevant to the argument though. To expound upon a point already made in the passage is not a explanation of the point in the passage.

I agree that D should be the answer.

Hope I've validated in some way the poor reasoning of A.

Thanks,

Jared
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by reply2spg » Thu Jul 15, 2010 8:33 pm
This is tough for me. why B is wrong?
arora007 wrote:source: McGraw Hill's Conquering GMAT Verbal and writing

Most biologists agree that evolution takes place extremely
slowly, with species requiring millions and millions of years
to accumulate enough small changes to gradually transform
into new ones. For the �rst 4 billion years of Earth's his-
tory, the only species known were bacteria, plankton, and
algae. But the fossil record indicates that during a brief
30 million year span known as the Cambrian explosion, the
eventual lineages of all major animal groups alive today
appeared.
Which of the following, if true, provides at least a partial
explanation for the discrepancy outlined above?
A. The fossil record only represents a small portion of the species
alive at any given time.
B. The fossil record indicates a number of major extinction events
in Earth's history.
C. Some of the lineages found in the fossil record of the Cambrian
explosion are no longer alive today.
D. Bacteria, plankton, and algae leave little evidence in the fossil
record because of their physical structures.
E. The fossil record indicates a large diversity in the plant species
inhabiting the Earth during the Cambrian explosion.

If you choose a choice please explain why.

OA-A
Sudhanshu
(have lot of things to learn from all of you)
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