Ecological roles of fungi — Why are fungi important in ecosystems and agriculture?

Introduction / Context:
Fungi influence ecosystems at multiple levels. As decomposers, they recycle carbon, nitrogen, and minerals; as pathogens, they shape plant communities and agricultural yields. Understanding these dual roles is foundational in ecology, forestry, and plant pathology.

Given Data / Assumptions:

• Many fungi are saprotrophs that decompose complex organics (cellulose, lignin).
• Numerous fungi cause economically significant plant diseases.
• Question asks whether both contributions are valid.

Concept / Approach:
Fungal hyphae and extracellular enzymes break down tough polymers, returning nutrients to soils. Conversely, rusts, smuts, mildews, wilts, and blights are fungal diseases that reduce crop productivity. Both roles coexist, making fungi ecologically indispensable yet sometimes agriculturally harmful.

Step-by-Step Solution:

Verification / Alternative check:
Soil respiration studies and crop loss reports corroborate these complementary impacts of fungi.

Why Other Options Are Wrong:

• Only (a) or only (b) is incomplete; fungi perform both functions.
• None of the above ignores well-established ecological facts.

Common Pitfalls:
Overgeneralizing fungi as purely harmful or purely beneficial; their roles are context-dependent.

Final Answer:
Both (a) and (b)