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Question #46603
The Question
A population of cotton bollworms rapidly evolves resistance to transgenic Bt cotton expressing the cryIAc gene. Based on the principles of evolutionary ecology and the mechanism of Cry protein action, which of the following best describes the physiological basis of this resistance and its subsequent ecological trade-off in a non-transgenic (refuge) crop area?
Options
- A.
The insects develop an acidic midgut pH to prevent protoxin solubilization, resulting in a higher reproductive output in non-transgenic areas due to conserved metabolic energy.
- B.
The insects acquire mutations altering specific midgut epithelial receptors, preventing toxin binding, but suffer reduced fecundity in non-transgenic areas due to the metabolic cost of resistance.
- C.
The insects utilize systemic RNA interference (RNAi) to neutralize the ingested cry mRNA, maintaining equal ecological fitness across both transgenic and non-transgenic fields.
- D.
The insects upregulate alkaline proteases that completely degrade the active toxin into amino acids, giving them a competitive survival advantage over wild-type pests in all environments.
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
Ecological Fitness (Darwinian Fitness)|Evolutionary Ecology of Parasitism|Cry Gene Specificity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the mechanism of Bt toxin (alkaline pH, midgut pores) but fail to integrate it with evolutionary biology (directional selection and the cost of resistance).
The primary trap is Option C, which exploits functional confusion by mixing up the two major NCERT pest-resistance strategies (Bt vs RNAi).
Another trap is failing to recognize that evolutionary adaptations like toxin resistance almost always carry a metabolic penalty (reduced fitness) in environments where the selective pressure (the toxin) is absent.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Organisms and Populations - Class 12 |
| Concept | Ecological Fitness (Darwinian Fitness) |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |