Here's a breakdown:
* Polygenic trait: A trait controlled by multiple genes, resulting in a continuous range of phenotypes (e.g., height, skin color).
* Stabilizing selection: Favors the average phenotype, selecting against extreme variations. This results in a narrowing of the distribution of traits within a population.
Example:
Imagine a population of birds where beak size is a polygenic trait. If the environment favors birds with medium-sized beaks for efficient seed cracking, birds with very small or very large beaks will have lower survival rates. Over time, stabilizing selection will eliminate the extreme phenotypes, leading to a population with mostly medium-sized beaks.
Key points:
* Stabilizing selection reduces genetic variation.
* It shifts the average value of a trait towards the middle of the distribution.
* It favors intermediate phenotypes and selects against extreme phenotypes.
Other types of natural selection include:
* Directional selection: Favors one extreme phenotype, shifting the average value in that direction.
* Disruptive selection: Favors both extreme phenotypes, leading to a bimodal distribution.
