Q2 - When the ancient fossils...

[ohthatpatrick]

Question Type:
Weakens

Stimulus Breakdown:
Conclusion: The discovery of a native NZ mammal shows that "lack of competition from mammals" is not the cause of the rich and varied NZ bird population.
Evidence: We thought NZ didn't have any native land mammals, but it looks like it does.

Answer Anticipation:
It is possible to reconcile the PREM with the ANTI-CONC?

Is it possible that NZ did indeed have at least one type of native land mammal, but it's still true that NZ birds flourished due to lack of competition from mammals?

It seems like if we only know of one mammal species, that one mammal species probably wouldn't have made a huge impact on the birds, so the birds still would have enjoyed a lack of competition. Maybe the mammal lived in a different area from the birds, or it ate different food or just somehow didn't mess with anything the birds need/want to flourish.

Correct Answer:
B

Answer Choice Analysis:
(A) This strengthens. The more mammals, the more competition, the more the author seems right.

(B) YES! This'll do. This allows us to reconcile the PREM (there was a land mammal) with the ANTI-CONC (a lack of competition from mammals allowed birds to flourish). This land mammal had no effect on birds, since it was long gone before the birds arrived.

(C) Out of scope. We only care about "competition from mammals".

(D) We don't know if NZ is a country with rich and varied native land mammals, so this fact isn't going to tell us anything about what was going on in NZ.

(E) This has nothing to do with whether birds on NZ had any competition from NZ land mammals.

Takeaway/Pattern: Like most Weaken questions, the most effective way to prime your brain for the answers is simply to say
GIVEN THAT I HAVE TO ACCEPT [prem],
HOW CAN I ARGUE [anti-conc]?

GIVEN THAT "NZ did have at least one native land mammal",
HOW CAN WE ARGUE that "NZ birds flourished due to a lack of competition from mammals?"

#officialexplanation

[fadams]

It is not true that native birds rich population is due to lack of competition
Because evidence suggest that mammals existed on the island where the birds are.

Assumes: if there is evidence to suggest mammals, then birds had competition
Overlooks the possibility that even if the evidence suggest mammals existed, something else can suggest that the birds in fact had no competition

A. Speaks to the amount of possibly mammals doesn’t change things
B. If true, that recently discovered land mammals become extinct before the native birds were established, then it indeed possible that native birds is rich in population independent of mammal competition.
C. Again speaks to other species, now reptiles instead of mammals
D. Discusses countries with rich and varied native land mammals, which is a scope irrelevant
E. Discusses other islands. Irrelevant

[maryadkins]

Thank you for your explanation.

To elaborate a bit:

(C) is not wrong because it brings in reptiles necessarily. Strengthen/weaken questions often bring in outside information. (C) is wrong because it doesn't tell us what this would have to do with competition.

Likewise, (D) doesn't tell us what this would have to do with competition.

(B), the correct answer, destroys the idea that the land mammals were competing with the birds. They existed at different times and did not overlap.