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Difficulty: HardLogical Inferences

Stomatal density on the leaves of *Ginkgo biloba* is inversely proportional to atmospheric carbon dioxide (CO2CO_2) concentrations, a relationship widely utilized by paleoclimatologists to reconstruct ancient climates. However, recent chamber experiments demonstrate that when *G. biloba* saplings are grown under highly fluctuating diurnal temperatures, their stomatal development becomes erratic, decoupling from CO2CO_2 levels and exhibiting highly variable densities that mimic both hyper-arid and humid ancient profiles. Consequently, fossilized leaf samples of *G. biloba* collected from geological strata associated with high-frequency thermal instability may lead to erroneous climate reconstructions unless researchers can verify that ______

Which choice most logically completes the text?

  1. A
    mature *G. biloba* trees are entirely resistant to the temperature-induced stomatal development errors observed in saplings.
  2. diurnal temperature fluctuations during the period of leaf development were not severe enough to decouple stomatal density from carbon dioxide levels.Answer
  3. C
    fluctuations in diurnal temperatures are historically followed by proportional shifts in atmospheric carbon dioxide concentrations.
  4. D
    the stomatal development of other fossilized plant species in the same geological strata was similarly disrupted by temperature changes.

Answer

The correct answer is that diurnal temperature fluctuations during the period of leaf development were not severe enough to decouple stomatal density from carbon dioxide levels.
The correct answer is supported because the passage states that temperature fluctuations decouple stomatal development from carbon dioxide levels, causing erratic profiles that mimic other climates. To ensure a reconstruction is not erroneous, researchers must verify that such decoupling fluctuations did not occur during the growth period of the sampled leaves.

Step-by-Step Solution

1
Identify the primary premise.
Stomatal density in *Ginkgo biloba* is a standard proxy for atmospheric carbon dioxide concentrations.
This establishes the baseline methodology of the paleoclimatologists.
2
Identify the interfering variable.
Fluctuating diurnal temperatures disrupt this development, decoupling stomatal density from carbon dioxide levels.
This shows why the baseline methodology might fail in certain environments.
3
Determine the condition needed to validate the methodology.
Researchers must rule out the disruptive effect of temperature fluctuations in the strata being studied.
If the temperature fluctuations were not severe enough to cause decoupling, the stomatal density proxy remains valid.

Key Concept

Drawing logical inferences from experimental scientific premises
Estimated Time:2m 0s
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Topics

Logical Inferences

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