[Campbell Biology P.677] Based on the data in the table, which statement best describes the ... | Practice Question

Based on the data in the table, which statement best describes the effect of moss on K⁺ weathering from granite and andesite?

  • A: Moss significantly increased K⁺ weathering from granite (from 0.68 to 1.72 µmol), but only slightly from andesite (from 0.60 to 0.92 µmol).
  • B: Moss decreased K⁺ weathering from both granite and andesite.
  • C: Moss had a similar significant increase on K⁺ weathering from both rock types.
  • D: Moss increased K⁺ weathering from andesite more than from granite.

Explanation

To determine the net effect of moss, we sum the amount released in water in the experimental microcosms and the amount taken up by moss, and then compare this total to the amount released in the control microcosms. For granite, K⁺ released in control was 0.68 µmol. In experimental, 0.65 µmol was released in water and 1.07 µmol was taken up by moss, for a total of 1.72 µmol. The increase is 1.72 - 0.68 = 1.04 µmol. For andesite, K⁺ released in control was 0.60 µmol. In experimental, 0.64 µmol was released in water and 0.28 µmol was taken up by moss, for a total of 0.92 µmol. The increase is 0.92 - 0.60 = 0.32 µmol. Thus, moss significantly increased K⁺ weathering from granite more than from andesite.