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Difficulty: HardIdentifying Necessary Assumptions

Ornithologist: The endangered Kakapo bird relies almost entirely on the fruit of the Rimu tree for breeding. In fact, Kakapos only attempt to breed during years when the Rimu tree produces a massive abundance of fruit, an event known as "mast seeding." Climate models predict that rising average temperatures will cause Rimu trees to mast seed every two years over the next century, rather than their historical average of once every five years. Therefore, the frequency of Kakapo breeding seasons will significantly increase over the next century.

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

  1. Kakapos do not require a biological recovery period between breeding attempts that is substantially longer than two years.Answer
  2. B
    If a Rimu tree produces a massive abundance of fruit, the Kakapo will always attempt to breed during that year.
  3. C
    The rising average temperatures predicted by climate models will not alter the nutritional composition of the Rimu fruit.
  4. D
    The total population of Kakapo birds will significantly increase over the next century as a result of the changing climate.
  5. E
    The historical five-year cycle of Rimu tree mast seeding was caused exclusively by the historical stability of average temperatures.

Answer

The assumption that Kakapos do not require a biological recovery period substantially longer than two years.
The correct answer bridges the gap between the environmental availability of the fruit and the biological capability of the bird. The argument relies on the premise that Kakapos only breed when the Rimu tree mast seeds, making mast seeding a necessary condition. However, just because this necessary condition will occur more frequently (every two years) does not guarantee the birds can exploit it. If the Kakapos require a biological recovery period of three or four years between breeding attempts, the increased frequency of mast seeding would not lead to a corresponding increase in breeding seasons. By stating that they do not require a recovery period longer than two years, this assumption is strictly logically required for the conclusion to hold.

Step-by-Step Solution

1
Identify the conclusion of the argument.
The frequency of Kakapo breeding seasons will significantly increase over the next century.
This is the ornithologist's final predictive claim, signaled by the keyword 'Therefore'.
2
Identify the premises supporting the conclusion.
Kakapos only breed during mast seeding years (making it a necessary condition). Climate change will increase mast seeding frequency from every 5 years to every 2 years.
These facts form the foundation of the author's prediction.
3
Analyze the logical gap between the premises and the conclusion.
The argument assumes that environmental resource availability (fruit) is the only barrier to more frequent breeding, ignoring the birds' biological capacity.
Just because a required resource appears more frequently does not mean the organism is biologically capable of utilizing it more frequently.
4
Apply the Negation Test to the choices.
Negating the correct statement ('Kakapos DO require a recovery period substantially longer than two years') completely undermines the conclusion.
If the birds biologically cannot breed every two years, the increased frequency of mast seeding will not lead to a significant increase in breeding seasons.

Key Concept

Applying the Negation Test to identify gaps between environmental conditions and biological capabilities.
Estimated Time:2m 0s
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Topics

Identifying Necessary Assumptions

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