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Question #46276
The Question
A plant species belonging to the family Fabaceae possesses the floral formula: % K(5) C1+2+(2) A(9)+1 G1. It relies exclusively on a specific bee species for pollination, representing a highly specialized (+/+) mutualistic interaction. Following a sudden ecological shift that causes the complete extinction of this pollinator, the plant population survives over evolutionary time by adopting a strategy of strict reproductive assurance. Which of the following represents the most probable evolutionary modification in its floral biology and the corresponding rationale?
Options
- A.
The flowers become cleistogamous, rendering the metabolically expensive zygomorphic corolla (%) and vexillary aestivation obsolete, as obligate autogamy ensures seed set.
- B.
The flowers transition to anemophily, characterized by the loss of the standard petal (C1) and the conversion of the diadelphous androecium to a polyandrous state.
- C.
The plant shifts to geitonogamy by developing actinomorphic flowers, allowing wind to transfer pollen between different flowers on the same plant.
- D.
The keel petals (C(2)) unfurl to expose the stamens and stigma, promoting xenogamy through a newly established commensal (+/0) interaction with wind.
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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
Fabaceae Floral Formula|Biotic Interactions - Positive/Negative sign matrix|Co-evolution
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question tests the synthesis of 'Morphology of Flowering Plants' (Fabaceae floral formula and papilionaceous corolla) with 'Sexual Reproduction in Flowering Plants' (cleistogamy and reproductive assurance) and 'Organisms and Populations' (mutualism).
The common misconception is failing to recognize that complex floral structures are metabolically expensive and are only maintained by the selective pressure of a +/+ biotic interaction.
When the pollinator is lost, the immediate evolutionary rescue mechanism is obligate autogamy (cleistogamy), rendering the zygomorphic adaptations obsolete.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Morphology of Flowering Plants - Class 11 |
| Concept | Fabaceae Floral Formula |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |