- PowerScore Staff
- Posts: 8950
- Joined: Feb 02, 2011
- Sat May 20, 2017 8:35 am
#35162
Complete Question Explanation
Weaken. The correct answer choice is (B)
Here, the author addresses the impact of a fossil discovery on a theory about why New Zealand’s
bird population is so rich and varied. It had been thought that New Zealand’s native bird population
was so rich and varied because it had no competition from mammals. But the discovery of the
ancient fossils of a primitive land mammal show that at one time New Zealand had indigenous land
mammals, contrary to the earlier belief that New Zealand had no native land mammals. Based on
this discovery, the author concludes that the theory that the native bird population is rich and varied
because it had no competition from mammals is false.
As always, paying close attention to the author’s word choice can give us more insight into the
validity of the argument. Here, the author tells us that the fossil discovery shows that New Zealand
“had once had” native land mammals. However, we do not know when those mammals existed, and
so we have no way to know whether those mammals ever competed with the native bird population.
The author merely assumes that the mammals and birds were in competition at some point.
This is a Weaken question. Our prephrase is that the correct answer choice will address the lack of
evidence that the mammals and birds ever actually competed with one another.
Answer choice (A): This answer choice provides additional support for the premise that New
Zealand had ancient indigenous land mammals. However, it ultimately has no effect on the
conclusion, because it does not tell us whether the mammals and birds were ever in competition.
Answer choice (B): This is the correct answer choice, since it addresses the issue of timing at the
heart of the author’s assumption. This choice makes clear that the newly discovered mammal and the
native birds never competed with one another, because the mammal became extinct before the native
bird population was established.
Answer choice (C): The existence of these other species is irrelevant to the question of whether the
native bird population was ever in competition with the native land mammals.
Answer choice (D): Here, the answer choice supports the general idea that the rich and varied land
mammal and bird populations may be incompatible, but it does not affect the conclusion in this
stimulus, which was about the effect of a certain land mammal species in New Zealand on the native
bird population in New Zealand.
Answer choice (E): This answer choice supports the idea that prior theories about the existence of
native land mammals may be proven incorrect. However, it does not address whether New Zealand’s
native bird and mammal species where ever in competition with each other.
Weaken. The correct answer choice is (B)
Here, the author addresses the impact of a fossil discovery on a theory about why New Zealand’s
bird population is so rich and varied. It had been thought that New Zealand’s native bird population
was so rich and varied because it had no competition from mammals. But the discovery of the
ancient fossils of a primitive land mammal show that at one time New Zealand had indigenous land
mammals, contrary to the earlier belief that New Zealand had no native land mammals. Based on
this discovery, the author concludes that the theory that the native bird population is rich and varied
because it had no competition from mammals is false.
As always, paying close attention to the author’s word choice can give us more insight into the
validity of the argument. Here, the author tells us that the fossil discovery shows that New Zealand
“had once had” native land mammals. However, we do not know when those mammals existed, and
so we have no way to know whether those mammals ever competed with the native bird population.
The author merely assumes that the mammals and birds were in competition at some point.
This is a Weaken question. Our prephrase is that the correct answer choice will address the lack of
evidence that the mammals and birds ever actually competed with one another.
Answer choice (A): This answer choice provides additional support for the premise that New
Zealand had ancient indigenous land mammals. However, it ultimately has no effect on the
conclusion, because it does not tell us whether the mammals and birds were ever in competition.
Answer choice (B): This is the correct answer choice, since it addresses the issue of timing at the
heart of the author’s assumption. This choice makes clear that the newly discovered mammal and the
native birds never competed with one another, because the mammal became extinct before the native
bird population was established.
Answer choice (C): The existence of these other species is irrelevant to the question of whether the
native bird population was ever in competition with the native land mammals.
Answer choice (D): Here, the answer choice supports the general idea that the rich and varied land
mammal and bird populations may be incompatible, but it does not affect the conclusion in this
stimulus, which was about the effect of a certain land mammal species in New Zealand on the native
bird population in New Zealand.
Answer choice (E): This answer choice supports the idea that prior theories about the existence of
native land mammals may be proven incorrect. However, it does not address whether New Zealand’s
native bird and mammal species where ever in competition with each other.