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Question #46578
The Question
In a highly eutrophic lake with a massive influx of sewage, the native fish population experiences rapid and indiscriminate mortality due to endemic endoparasitic infections. This deviates from the typical ecological principle where parasites co-evolve to avoid killing their hosts prematurely. Which of the following best explains this breakdown of the host-parasite continuum?
Options
- A.
Hypoxia-induced physiological stress lowers the host's immune threshold, disrupting stable co-evolution and favoring rapid parasitic replication.
- B.
Elevated Biochemical Oxygen Demand (BOD) directly induces horizontal gene transfer in parasites, permanently increasing their inherent virulence.
- C.
The parasites shift from an r-selected to a K-selected reproductive strategy to maximize resource extraction from the dying host.
- D.
Biomagnification of the organic waste selectively destroys the host's lymphoid organs, forcing the parasites to become free-living.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Evolutionary Ecology of Parasitism|BOD (Biochemical Oxygen Demand) Logic
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the NCERT line 'parasites evolve to be relatively harmless to the host' as an absolute rule, failing to realize that environmental stress (like high BOD/hypoxia) can disrupt this co-evolutionary equilibrium.
Additionally, this question tests the ability to distinguish between the ecological consequences of organic pollution (eutrophication/BOD) and non-biodegradable pollutants (biomagnification), a common trap in NEET Ecology.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Microbes in Human Welfare - Class 12 |
| Concept | BOD (Biochemical Oxygen Demand) Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |