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Question #46628
The Question
In a specific host-parasite interaction, a trematode induces 'parasitic castration' in its snail host. The infected snails exhibit significant somatic gigantism but completely lose their reproductive capacity. Which of the following statements correctly describes the ecological consequence of this interaction on the host population dynamics?
Options
- A.
The intrinsic rate of natural increase (r) becomes negative, resulting in an urn-shaped age pyramid, and the population will eventually crash despite the increased lifespan of infected individuals.
- B.
The host population's carrying capacity (K) increases due to enhanced somatic growth, leading to an asymptote in the logistic growth curve at a higher population density.
- C.
The population age pyramid becomes bell-shaped because the energy previously used for reproduction is now perfectly reallocated to maximize host survival.
- D.
The exponential growth model (dN/dt = rN) remains applicable as the decrease in birth rate (b) is exactly offset by the decrease in death rate (d) due to gigantism.
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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
Pioneer_Species|Nutrient_Immobility|Biomass_Accumulation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between individual somatic fitness and population reproductive fitness.
Students often fall for the trap that increased host size (gigantism) and survival equate to population stability.
The core NCERT concept tested is that population growth (r) and age pyramids are strictly dependent on birth rates (b), which are decimated by parasitic castration, inevitably leading to an urn-shaped pyramid and population crash.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Organisms and Populations - Class 12 |
| Concept | Birth/Death Rate vs Immigration/Emigration |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |