Before You Begin
Question #46182
The Question
A novel water-soluble environmental contact toxin causes rapid systemic toxicity and mass mortality in a population of frogs, but fails to affect lepidopteran pests in the same ecosystem unless the toxin is ingested. Which of the following physiological constraints best explains this differential susceptibility, and how does it parallel the efficacy of Bacillus thuringiensis (Bt) toxin?
Options
- A.
Frogs require a highly permeable, moist integument for cutaneous respiration, facilitating rapid toxin absorption, whereas insects possess an impermeable chitinous cuticle, necessitating ingestion for toxins like Bt protoxin to reach the alkaline gut.
- B.
Frogs possess a highly vascularized epidermis that actively transports toxins, whereas insects have a waxy cuticle and an acidic gut that neutralizes contact toxins before they reach the hemolymph.
- C.
The amphibian skin lacks the alkaline pH required to neutralize the toxin, whereas the insect cuticle secretes alkaline fluids that solubilize and detoxify contact poisons like Bt toxin.
- D.
Frogs absorb the toxin through their pulmonary epithelium during positive pressure breathing, whereas insects use a tracheal system that filters out water-soluble toxins before they reach the tissues.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Amphibian Integument | Bt Toxin Activation Trigger | Cry Gene Specificity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'Bt toxin requires an alkaline gut' without understanding the structural biology reason WHY it must be ingested in the first place (the impermeable chitinous cuticle barrier).
This question forces the student to synthesize structural organization across taxa (Amphibia vs Insecta) with biotechnology (Bt toxin mechanism), highlighting the evolutionary trade-off where the amphibian requirement for cutaneous gas exchange creates a fatal vulnerability to contact pollutants.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Amphibian Integument |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |