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# Birds have been said to be descended from certain birdlike dinosaur

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Re: Birds have been said to be descended from certain birdlike dinosaur [#permalink]

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03 Mar 2018, 16:23
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AbdurRakib wrote:
Birds have been said to be descended from certain birdlike dinosaur species with which they share distinctive structural features. The fossil record, however, shows that this cannot be so, since there are bird fossils much older than the earliest birdlike dinosaur fossils that have been found.

Which of the following is an assumption on which the argument relies?

A) The birdlike dinosaurs have no descendants.
B) There are no flightless dinosaur species that have the distinctive structural features shared by birds and birdlike dinosaurs.
C) There are no birdlike dinosaur fossils that are older than the bird fossils but have not yet been unearthed.
D) It could not have been the case that some birds were descendant from one of the bird like dinosaur species and other birds from another.
E) Birds cannot have been descended from dinosaur species with which the birds do not share the distinctive structural features.

OG 2017 New Question

This is an assumption question.

PREMISE: Some believe that birds descended from dinosaurs
PREMISE: There are bird fossils much older than the earliest birdlike dinosaur fossils found.
CONCLUSION: Birds did NOT descend from birdlike dinosaurs

First try to identify an assumption that the author needs in order for the conclusion be valid.
If you can't think of one, you may need to resort to the negation method
So, we'll negate each answer choice.
The answer choice that, when negated, DESTROYS the argument will be the correct answer.

A) The birdlike dinosaurs do have descendants.
Does this destroy the conclusion that Birds did NOT descend from birdlike dinosaur?
No. It makes no difference where the birdlike dinosaurs came from.
ELIMINATE A

B) There ARE flightless dinosaur species that have the distinctive structural features shared by birds and birdlike dinosaurs.
Does this destroy the conclusion that Birds did NOT descend from birdlike dinosaur?
No, the argument is about whether birds have DESCENDED from birdlike dinosaurs.
ELIMINATE B

C) There ARE birdlike dinosaur fossils that are older than the bird fossils but have not yet been unearthed.
Does this destroy the conclusion that Birds did NOT descend from birdlike dinosaur?
YES! The author's argument is based on the fact that there are no discovered birdlike dinosaur fossils that are older than bird fossils.
So, if there ARE birdlike dinosaur fossils that are older than the bird fossils, then this KILLS the author's conclusion.
KEEP C

D) It COULD have been the case that some birds were descendant from one of the bird like dinosaur species and other birds from another.
Does this destroy the conclusion that Birds did NOT descend from birdlike dinosaur?
No. The word COULD doesn't have the certainty required to destroy an argument.
ELIMINATE D

E) Birds MAY have descended from dinosaur species with which the birds do not share the distinctive structural features.
Does this destroy the conclusion that Birds did NOT descend from birdlike dinosaur?
No. The conclusion is all about birds descending from birdlike dinosaurs
ELIMINATE E

Cheers,
Brent
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Re: Birds have been said to be descended from certain birdlike dinosaur [#permalink]

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15 May 2018, 09:38
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AbdurRakib wrote:
Birds have been said to be descended from certain birdlike dinosaur species with which they share distinctive structural features. The fossil record, however, shows that this cannot be so, since there are bird fossils much older than the earliest birdlike dinosaur fossils that have been found.

Which of the following is an assumption on which the argument relies?

A) The birdlike dinosaurs have no descendants.
B) There are no flightless dinosaur species that have the distinctive structural features shared by birds and birdlike dinosaurs.
C) There are no birdlike dinosaur fossils that are older than the bird fossils but have not yet been unearthed.
D) It could not have been the case that some birds were descendant from one of the bird like dinosaur species and other birds from another.
E) Birds cannot have been descended from dinosaur species with which the birds do not share the distinctive structural features.

OG 2017 New Question

There is a small mistake in option a missing living which needed to be along with descendants .

Posted from my mobile device
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Posts: 47015
Re: Birds have been said to be descended from certain birdlike dinosaur [#permalink]

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15 May 2018, 09:46
tejyr wrote:
AbdurRakib wrote:
Birds have been said to be descended from certain birdlike dinosaur species with which they share distinctive structural features. The fossil record, however, shows that this cannot be so, since there are bird fossils much older than the earliest birdlike dinosaur fossils that have been found.

Which of the following is an assumption on which the argument relies?

A) The birdlike dinosaurs have no descendants.
B) There are no flightless dinosaur species that have the distinctive structural features shared by birds and birdlike dinosaurs.
C) There are no birdlike dinosaur fossils that are older than the bird fossils but have not yet been unearthed.
D) It could not have been the case that some birds were descendant from one of the bird like dinosaur species and other birds from another.
E) Birds cannot have been descended from dinosaur species with which the birds do not share the distinctive structural features.

OG 2017 New Question

There is a small mistake in option a missing living which needed to be along with descendants .

Posted from my mobile device

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Thank you. Edited.
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Re: Birds have been said to be descended from certain birdlike dinosaur   [#permalink] 15 May 2018, 09:46

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