Before You Begin
Question #46631
The Question
According to Allen's Rule, mammals in colder climates adapt by reducing the size of their extremities to minimize heat loss. If an obligate ectoparasite relies entirely on such a cold-climate mammalian host for thermal stability and habitat, which of the following morphological adaptations would be most strongly selected for in the ectoparasite, and why?
Options
- A.
Spherical body morphology; to decrease the ectoparasite's own surface area-to-volume ratio and independently conserve its metabolic heat.
- B.
Dorsoventrally flattened body morphology; to maximize surface area contact with the host's skin for conductive heat transfer and secure attachment.
- C.
Elongated, cylindrical body morphology; to penetrate the thick insulating blubber layer of the host for direct access to deep blood vessels.
- D.
Complete loss of the digestive system; to compensate for the high metabolic cost of surviving in sub-zero environmental temperatures.
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
Parasitism|Co-extinction Logic|Specialized Host-Parasite Relationship
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often misapply Allen's Rule directly to the parasite, assuming the parasite itself should become spherical to conserve heat (Option A).
The critical realization is that the parasite's microhabitat is the host's skin; therefore, its morphology must adapt to maximize heat transfer FROM the host (requiring a flattened shape) rather than isolating itself from the environment.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Organisms and Populations - Class 12 |
| Concept | Evolutionary Ecology of Parasitism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |