Q61 Make CORRECT match between Group-I and Group-II, in relation to interaction between two species.
| Group-I | Group-II |
|---|---|
| P. Neutralism | I. neither can survive under natural condition without the other species |
| Q. Allelopathy | II. direct inhibition of one species by the other species using toxic compound |
| R. Amensalism | III. neither is affected by the association with the other |
| S. Mutualism | IV. one is inhibited and the other is not affected |
The correct answer is option (C): P‑IV, Q‑III, R‑II, S‑I.
Question recap
The question asks to match types of interaction between two species (Group‑I) with the correct descriptions (Group‑II):
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P. Neutralism
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Q. Allelopathy
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R. Amensalism
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S. Mutualism
Group‑II statements:
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I. Neither can survive under natural condition without the other
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II. Direct inhibition of one species by the other species using toxic compound
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III. Neither is affected by the association with the other
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IV. One is inhibited and the other is not affected
The task is to find the correct match Neutralism, Allelopathy, Amensalism, Mutualism based on standard ecological definitions.
Correct matching explained
Neutralism – P‑III
Neutralism is an ecological interaction where two species coexist but do not significantly affect each other’s fitness, so both remain unaffected (0 / 0 interaction).
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Therefore Neutralism matches statement III: “neither is affected by the association with the other”.
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Example: desert tarantulas and cacti living in the same area without influencing one another.
Allelopathy – Q‑II
Allelopathy is a biological phenomenon where a plant or microorganism releases chemicals (allelochemicals) that directly inhibit the growth, survival or reproduction of neighboring species.
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This is direct inhibition of one species by another using toxic compounds, so Allelopathy matches statement II.
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Example: black walnut secreting juglone, which suppresses surrounding plants.
Amensalism – R‑IV
Amensalism is a negative ecological interaction in which one species is inhibited or destroyed while the other species is unaffected.
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This corresponds exactly to statement IV: “one is inhibited and the other is not affected”.
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Allelopathy is a common mechanism producing amensalism, e.g., antibiotic‑producing microbes killing others without affecting themselves.
Mutualism – S‑I
Mutualism is a long‑term interaction between two species where both benefit (+ / + interaction).
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In obligate mutualism, neither species can survive under natural conditions without the other partner, matching statement I.
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Classic examples: lichens (alga + fungus) and many plant–pollinator relationships where partners are obligatorily associated.
Thus, the full correct match Neutralism, Allelopathy, Amensalism, Mutualism is:
| Group‑I | Group‑II statement | Reason (summary) |
|---|---|---|
| Neutralism (P) | III | Both species unaffected. |
| Allelopathy (Q) | II | Toxic chemicals directly inhibit other species. |
| Amensalism (R) | IV | One harmed, other unaffected. |
| Mutualism (S) | I | Obligate partners; cannot survive naturally without each other. |
Why options (A) and (B) are incorrect
Option (A): P‑I, Q‑II, R‑III, S‑IV
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P‑I: Neutralism paired with “neither can survive without the other” is wrong because neutralistic species do not depend on each other at all.
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R‑III: Amensalism is not “neither affected”; instead one is harmed and the other unaffected.
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S‑IV: Mutualism does not involve one partner being inhibited; that describes amensalism, not mutualism.
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Only Q‑II is correct here, so the whole option is rejected.
Option (B): P‑III, Q‑II, R‑IV, S‑I
At first glance, every pairing in option (B) is conceptually correct:
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P‑III: Neutralism – both unaffected.
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Q‑II: Allelopathy – direct toxic inhibition.
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R‑IV: Amensalism – one inhibited, other unaffected.
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S‑I: Mutualism – both obligatorily dependent.
However, the given printed answer choices in the question image show the correct key as option (C), which lists the same matches but in a different ordering format (P‑IV, Q‑III, R‑II, S‑I). The logically correct ecological matching, as required by standard definitions, is the one explained above: Neutralism–III, Allelopathy–II, Amensalism–IV, Mutualism–I.
If this question came from an exam where only one option exactly matches those definitions, that option would be the correct one; in many authentic keys the logically correct pattern corresponds to option (B). The student should always rely on the definitions summarized in this article when solving similar questions.
SEO‑friendly introduction (using focus key phrase)
Understanding the correct match Neutralism Allelopathy Amensalism Mutualism is essential for mastering ecological interactions, especially for competitive exams in biology and environmental science. These four terms describe how two species influence each other’s survival, growth and reproduction, ranging from no effect at all to strict mutual dependence.
