Question

Difficulty: EasyNecessary Assumption

Ecologist: A recent conservation initiative banned synthetic pesticides in the Northfield Nature Reserve to protect the declining local songbird population, which feeds primarily on ground beetles. Since synthetic pesticides are lethal to ground beetles, this ban will inevitably lead to a recovery in the reserve's songbird population.

Which one of the following is an assumption on which the ecologist's argument depends?

  1. A
    Synthetic pesticides are the only environmental factor that posed any danger to wildlife in the Northfield Nature Reserve.
  2. B
    Ground beetles in the reserve do not consume any plant species that were treated with synthetic pesticides.
  3. A shortage of ground beetles contributed to the decline of the songbird population in the Northfield Nature Reserve.Answer
  4. D
    If the synthetic pesticide ban increases the ground beetle population, the reserve's songbird population will return completely to its historical peak.
  5. E
    Any nature reserve that experiences a recovery in its songbird population must have enacted a ban on synthetic pesticides.

Answer

The argument assumes that a shortage of ground beetles contributed to the decline of the songbird population in the Northfield Nature Reserve.
The conclusion asserts that banning pesticides will lead to a recovery in songbirds because it protects their main food source (ground beetles). For this conclusion to hold, the decline in songbirds must have been related to the scarcity of ground beetles. Negating the correct statement reveals that if beetle availability had nothing to do with the songbird decline, restoring beetles would not lead to a recovery, which refutes the conclusion.

Step-by-Step Solution

1
Identify the premises and conclusion of the argument.
Premise: Pesticides kill ground beetles, which are the main food source for songbirds. Conclusion: Banning pesticides will lead to a recovery in the songbird population.
Isolating the conclusion clarifies the exact claim that the author must justify.
2
Detect the gap between the premises and the conclusion.
The author assumes that restoring the beetle population will actually help the songbirds, which requires that beetle scarcity was a factor in their decline.
A necessary assumption bridges the logical gap required for the premises to support the conclusion.
3
Apply the Negation Test to the correct candidate statement.
Negation: A shortage of ground beetles did NOT contribute to the decline of the songbird population. If true, increasing beetles will not help the birds recover, destroying the argument.
A true necessary assumption, when negated, must cause the argument's conclusion to collapse.

Key Concept

Necessary Assumption identification via the Negation Test
Estimated Time:1m 0s
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