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Question #46882
The Question
The maximum body size of terrestrial insects, such as Periplaneta americana, is evolutionarily constrained compared to vertebrates. Which of the following physiological limitations primarily dictates this 'metabolic ceiling' as the insect's body volume increases?
Options
- A.
The hemolymph in their open circulatory system lacks respiratory pigments, preventing the active transport of dissolved oxygen to deep visceral organs.
- B.
The tracheal system relies on simple diffusion, and as body volume increases, the oxygen demand outpaces the diffusion capacity due to a decreasing surface-area-to-volume ratio.
- C.
An increase in body size exponentially increases the surface-area-to-volume ratio, leading to fatal desiccation through the spiracular sphincters.
- D.
The chitinous exoskeleton becomes disproportionately heavy, requiring more ATP for locomotion than the spiracles can generate through anaerobic respiration.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Cockroach Respiratory Tracheal System|Allen’s Rule and Surface-to-Volume Ratio
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the roles of the open circulatory system and the tracheal system in insects.
A common misconception is that the lack of hemoglobin (Option A) limits their size.
However, the tracheal system evolved specifically to bypass the hemolymph for gas exchange.
The true limitation is the physics of diffusion (Fick's Law) applied to a decreasing surface-area-to-volume ratio as body size increases.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Structural Organisation in Animals - Class 11 |
| Concept | Cockroach Respiratory Tracheal System |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |