Answer:
A polygenic trait can be described as a physical trait which is influenced by more than one gene.
The three types of selection for a polygenic trait are:
1) Directional Selection: In a directional selection, one of the phenotype is favored in an ecosystem. As a result of this favoring, the allelic frequency changes and shifts in favor of this particular trait.
2) Stabilizing selection: It is a type of natural selection in which the intermediate trait is favored. The population carries a middle trait in abundance.
3) Disruptive Selection: Disruptive trait is a type of natural selection in which the traits on the extreme sides are favored. The intermediate traits are less favored.