Question

The IUCN Red List is based on a set of criteria to evaluate species vulnerability to extinction. Which one or more of the options is/are used as criteria?

• A. Absolute population size
• B. Geographic range
• C. Economic value
• D. Change in population size over time

Hint:

Think of mycorrhizae as a \textbf{trade}. If soil nutrients are scarce, the plant needs the trade (mutualism). If nutrients are abundant, the trade can turn \textbf{costly} (parasitism) or \textbf{neutral} (commensalism).

Answer 1

The Correct Option is A, B, D

Plant–Mycorrhizal Fungi Interactions

Step 1: Recall what mycorrhizae do.

Mycorrhizal fungi exchange soil nutrients (P, N, water) for photosynthate (carbon) from plant roots. The net effect depends on soil nutrient availability.

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Step 2: Classify interactions by cost–benefit to the plant.

• Nutrient-poor soils: Fungal hyphae enhance nutrient uptake. Plant gains more than it pays in carbon. \(\Rightarrow\) Mutualism → (C) true.
• Nutrient-rich soils: Plant can acquire nutrients without fungus; fungus still takes carbon. Plant pays cost with little or no return. \(\Rightarrow\) Parasitism → (A) true.
• Intermediate/neutral cases: Net plant effect ≈ 0 while fungus still gains carbon. \(\Rightarrow\) Commensalism → (D) can occur.

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Step 3: Eliminate the incorrect option.

(B) Predation involves killing or consuming another organism; mycorrhizal colonization does not fit this definition.

Final Answer: \[ \boxed{\text{(A) Parasitism, \quad (C) Mutualism, \quad (D) Commensalism}} \]