The correct answer is (C) P-3, Q-1, R-4, S-2.
Definitions
These ecological relationships describe interactions between two organisms in an ecosystem. Commensalism (P) occurs when one organism benefits while the other remains unaffected (+/0). Mutualism (Q) benefits both organisms (+/+). Parasitism (R) benefits one organism while harming the other (+/-). Amensalism (S) harms one organism while the other is unaffected (-/0).
Option Analysis
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(A) P-1, Q-2, R-3, S-4: Incorrect. P (commensalism) mismatches 1 (both benefited, which is mutualism).
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(B) P-2, Q-3, R-4, S-1: Incorrect. P mismatches 2 (one impeding other, amensalism); Q mismatches 3 (+/0).
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(C) P-3, Q-1, R-4, S-2: Correct. Matches exactly: P (+/0), Q (+/+), R (+/-), S (-/0).
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(D) P-1, Q-4, R-3, S-2: Incorrect. P mismatches 1 (+/+); Q mismatches 4 (+/-).
Ecosystems thrive on relationships between two organisms in an ecosystem, where species interact through symbiosis like commensalism, mutualism, parasitism, and amensalism. These biotic interactions shape survival, competition, and balance in nature—key for GATE Life Sciences and ecology exams.
Core Types Explained
Commensalism (+/0): One benefits (e.g., barnacles on whales for transport), the other unaffected.
Mutualism (+/+): Both gain (e.g., bees pollinating flowers for nectar).
Parasitism (+/-): Parasite benefits, host harmed (e.g., ticks on dogs).
Amensalism (-/0): One harmed (e.g., penicillin inhibiting bacteria), other neutral.
| Relationship |
Effect on Organism 1 |
Effect on Organism 2 |
Example |
| Commensalism (P) |
+ (benefits) |
0 (unaffected) |
Barnacles on whale |
| Mutualism (Q) |
+ |
+ |
Bee-flower pollination |
| Parasitism (R) |
+ |
– (harmed) |
Tick on mammal |
| Amensalism (S) |
– |
0 |
Alga inhibiting bacteria |
Matching Question Solved
In Group I (P: Commensalism, Q: Mutualism, R: Parasitism, S: Amensalism) vs. Group II (1: both benefited, 2: one impeding, 3: one benefits unaffected, 4: one benefited other harmed), option (C) P-3, Q-1, R-4, S-2 fits perfectly. This aligns with standard ecology: 3 for commensalism (+/0), 1 for mutualism (+/+), 4 for parasitism (+/-), 2 for amensalism (-/0).
Other options fail: (A) swaps benefits; (B) confuses impeding with neutral; (D) mismatches harmed/benefited.
For competitive exams like GATE Life Sciences, memorize via +/-0 notation for quick matching.
