Examkin

Question

Difficulty: EasyLogical Inferences

Many plants form symbiotic relationships with mycorrhizal fungi, which supply the plants with soil nutrients in exchange for carbon. While both arbuscular mycorrhizal (AM) fungi and ectomycorrhizal (ECM) fungi assist in nutrient uptake, they differ in how they impact soil carbon storage. AM fungi release glomalin, a glycoprotein that binds soil particles together and slows carbon decomposition. In contrast, ECM fungi produce enzymes that actively break down organic matter to access nitrogen (NN), a process that releases carbon dioxide (CO2CO_2) back into the atmosphere. Which choice most logically completes the text?

  1. A
    plants associated with ECM fungi will absorb significantly more carbon from the atmosphere than plants associated with AM fungi.
  2. B
    both types of fungi are equally effective at preventing carbon dioxide (CO2CO_2) from escaping into the atmosphere.
  3. C
    ECM fungi are highly efficient at obtaining nitrogen (NN) from the organic matter in the soil.
  4. soils dominated by AM fungi will typically accumulate and retain carbon more effectively than soils dominated by ECM fungi.Answer

Answer

soils dominated by AM fungi will typically accumulate and retain carbon more effectively than soils dominated by ECM fungi.
The correct answer is supported by the contrast established in the text. AM fungi slow carbon decomposition, which helps retain carbon in the soil, while ECM fungi break down organic matter and release carbon dioxide (CO2CO_2) into the atmosphere, reducing soil carbon storage. Therefore, soils containing predominantly AM fungi are expected to retain carbon more effectively than soils dominated by ECM fungi.

Step-by-Step Solution

1
Identify the core contrast presented in the passage.
AM fungi slow down carbon decomposition, whereas ECM fungi release carbon dioxide (CO2CO_2) by breaking down organic matter.
This establishes the opposing roles of the two types of fungi in the soil carbon cycle.
2
Determine the logical outcome of these contrasting processes on soil carbon storage.
Because AM fungi inhibit decomposition and ECM fungi promote the release of carbon dioxide (CO2CO_2), soils with more AM fungi will keep carbon in the soil, while soils with more ECM fungi will lose it.
This allows for a direct comparison of the overall carbon retention in soils dominated by each fungus type.
3
Evaluate the choices to find the one that directly matches this logical comparison.
The statement that soils dominated by AM fungi retain carbon more effectively than those dominated by ECM fungi is the only valid, non-speculative conclusion.
This choice directly synthesizes the facts in the passage without introducing unsupported assumptions.

Key Concept

Logical Inferences
Rate this question

Topics

Logical Inferences

More questions from this topic