GED Science TestLife ScienceHard
A biologist is studying a population of a certain species of plant in a forest. She observes that the plants exhibit a wide range of heights, from very short to very tall. Over several generations, she notices that both the very short and very tall plants are more successful at reproducing than plants of intermediate height. This pattern suggests which type of natural selection is occurring?
- AArtificial selection
- BDisruptive selection
- CDirectional selection
- DStabilizing selection
Show answer & explanationAnswer & explanation
Correct answer: B. Disruptive selection
Disruptive selection favors individuals at both extremes of the phenotypic range over intermediate phenotypes. In this scenario, both very short and very tall plants are more successful, indicating disruptive selection.
Why the other options are wrong
- A. Artificial selection is selection imposed by humans, not natural environmental pressures.
- C. Directional selection favors one extreme of the phenotypic range, shifting the population mean over time.
- D. Stabilizing selection favors intermediate phenotypes and acts against extreme variations.
Disruptive Selection
Disruptive selection (or diversifying selection) is a type of natural selection that simultaneously favors individuals at both extremes of the phenotypic range over intermediate phenotypes, often leading to a bimodal distribution within a population.
- Favors extreme phenotypes.
- Acts against intermediate phenotypes.
- Can lead to sympatric speciation.
Memory trick: Selection's Shapes: Stable, Shift, Split.