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Question #45829
The Question
In a stable, uniform forest ecosystem, a population of insects exhibits a classic bell-shaped curve for a polygenic trait (e.g., body coloration). A subset of this population expands its range into an adjacent ecotone, which is highly heterogeneous with distinct, contrasting microhabitats. Over several generations, which of the following best describes the expected shift in the phenotypic distribution curve and the underlying selective pressure in the ecotone?
Options
- A.
The peak of the curve shifts in one direction due to directional selection, favoring a single extreme phenotype adapted to the edge effect.
- B.
The curve bifurcates to form two distinct peaks due to disruptive selection, as intermediate phenotypes are selected against in the heterogeneous microhabitats.
- C.
The curve becomes narrower and taller due to stabilizing selection, as the ecotone enforces strict phenotypic uniformity.
- D.
The bell curve flattens completely into a uniform distribution due to genetic drift overriding natural selection in the transition zone.
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
Polygenic Inheritance Curve|Ecotone and Edge Effect|Evolutionary Chronology
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the three natural selection curves (Stabilizing, Directional, Disruptive) from the Evolution chapter but fail to link them to specific ecological scenarios from the Ecology unit.
The trap is failing to recognize that the spatial heterogeneity of an ecotone specifically drives disruptive selection on polygenic traits, splitting the standard bell curve, rather than just causing a directional shift.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Polygenic Inheritance Curve |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |