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Question #46225
The Question
A lineage of xerophytic plants, characterized by fleshy, flattened stems (phylloclades) that serve as organs of perennation and photosynthesis, colonizes a highly stable, resource-abundant mesic habitat. Over millions of years, the environment remains consistently favorable with no drought stress. According to evolutionary principles, what is the most likely morphological outcome for this lineage's stems, and why?
Options
- A.
The phylloclades will transition into massive underground corms to escape competitive exclusion, driven by directional selection.
- B.
The fleshy stem modifications will gradually atrophy due to relaxed selection, as the metabolic cost of maintaining xeric adaptations reduces fitness in a stress-free niche.
- C.
The stems will become increasingly succulent to maximize resource storage, illustrating the principle of stabilizing selection.
- D.
The phylloclades will remain morphologically unchanged because stem modifications for perennation are fixed, homologous traits.
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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
Stem_Modifications|Primary_Succession_Facilitation|Adaptive_Radiation_Logic
Why This Question Is Tricky
Common Mistakes
The 'Conceptual Pivot' is the synthesis of 'Relaxed Selection' and metabolic trade-offs.
Students often harbor the misconception of orthogenesis—believing that complex adaptations (like phylloclades) are permanent evolutionary 'upgrades'.
To solve this, they must integrate NCERT Morphology (the specific stress-response function of phylloclades) with NCERT Evolution (natural selection is strictly environment-dependent) to realize that removing an environmental stressor leads to the evolutionary loss of the corresponding adaptation due to its unnecessary metabolic burden.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Morphology of Flowering Plants - Class 11 |
| Concept | Stem Modifications |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |