A fourteen-year study of finches

Answer choices

1. A

   Bad Assumption4% picked this

   During drought conditions, the weather promotes the growth of plants that produce

   The passage says droughts produce large, hard seeds, not small hard seeds. This answer would actually undermine the drought story — if drought weather produces small hard seeds, that doesn't explain why large finches with big bills have a food advantage during droughts. Negation test: if drought weather doesn't produce small hard seeds, the argument is unaffected.

   4%
2. B

   Correct73% picked this

   A lengthy period of rainy weather results in fewer large, hard

   Why this is right

   This is the assumption the argument needs. The rainy-year story explains why large finches struggle: small seeds are abundant, but large finches can't eat them fast enough to meet their energy demands. That story only delivers a survival drop if large finches no longer have access to their normal food (large, hard seeds). Negation test: if rainy weather does not reduce large/hard seed production, large finches just keep eating their usual food, never have to switch to inefficient small-seed feeding, and the rainy-year survival drop doesn't happen. The conclusion that climate causes the survival differential collapses.

   Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

   73%
3. C

   Bad Assumption7% picked this

   In rainy periods, the small finches gather enough food to grow much larger and heavier, but their ultimate size is limited by their

   The argument doesn't need small finches to grow larger in rainy years. The argument is about survival rates, not about size changes. Negation test: even if small finches don't grow larger or heavier in rainy years, the conclusion (that climate drives survival differentials) still goes through.

   7%
4. D

   Bad Assumption9% picked this

   The Galapagos climate during this fourteen-year period had about as much dry weather as it

   The argument doesn't need the climate to be balanced between dry and wet. It only needs both kinds of weather to occur and to produce the described effects on survival. Negation test: even if the 14-year period had much more dry weather than wet, the survival differentials in each kind of year would still exist, and the conclusion still goes through.

   9%
5. E

   Bad Assumption7% picked this

   Small seeds do not have to be cracked open in order to be digested by any

   The argument doesn't require small seeds to be edible without cracking. Even if all finches need to crack small seeds to digest them, the rainy-year story still works: small finches can crack small seeds easily, large finches struggle to consume enough. Negation test: even if some seeds need to be cracked, the survival differential the argument predicts can still hold.

   7%