Q.43 The phenomenon where an organism lives at the expense of another organism by harming it but not
killing, is called
(A) Commensalism
(B) Predation
(C) Symbiosis
(D) Parasitism
Correct Answer: (D) Parasitism
The phenomenon describes a relationship where one organism (parasite) lives on or in another (host), deriving nutrients at the host’s expense by causing harm without typically killing it immediately.
Option Analysis
(A) Commensalism: One organism benefits (e.g., epiphytic orchids on trees gaining sunlight), while the other remains unharmed and unaffected. This lacks the harm element.
(B) Predation: A predator kills and consumes the prey (e.g., lion eating zebra), resulting in the prey’s death, unlike the non-lethal harm here.
(C) Symbiosis: Broad term for close species interactions; includes mutualism (both benefit), commensalism (one benefits, other unaffected), and parasitism (one benefits, other harmed). It does not specifically denote harm.
(D) Parasitism: Matches exactly—one benefits by harming the host (e.g., tapeworm in intestines absorbing nutrients, weakening but not killing the host). Common in biology exams like CSIR NET.
Parasitism represents a fundamental ecological interaction where one organism, the parasite, lives at the expense of another organism, the host, by harming it but not usually killing it outright. This phenomenon, central to understanding species relationships in molecular biology, genetics, and ecology, contrasts sharply with other interactions like commensalism or predation.
Key Features of Parasitism
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Parasite derives nutrients, shelter, or reproduction sites from the host, causing gradual harm such as nutrient depletion or tissue damage.
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Host survives long-term, allowing parasite persistence (e.g., malaria parasite Plasmodium in human red blood cells impairs oxygen transport without immediate death).
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Types include ectoparasites (on host surface, like lice) and endoparasites (internal, like hookworms).
Differences from Other Interactions
| Interaction | Beneficiary Effect | Host/Prey Effect | Example |
|---|---|---|---|
| Parasitism | Benefits (gains resources) | Harmed but not killed | Tapeworm in human gut |
| Commensalism | Benefits | Unaffected | Barnacles on whale |
| Predation | Benefits (feeds) | Killed | Lion vs. zebra |
| Symbiosis | Varies (broad category) | Varies | Lichens (mutualism subtype) |
Importance in Life Sciences
Parasitism drives evolutionary adaptations, like host immune responses in biotechnology applications (e.g., vaccine development). For CSIR NET aspirants, mastering this distinguishes it from neutral or lethal interactions, aiding ecology and microbiology sections. Real-world impacts include disease control in bioremediation.
