Here's why:

* Natural Selection: Natural selection is the process where organisms with traits better suited to their environment are more likely to survive and reproduce. This means they pass those advantageous traits to their offspring.

* Phenotype: A phenotype refers to the observable characteristics of an organism, like its physical appearance, behavior, and metabolic processes. These are the traits that are directly influenced by the environment.

* Genotype: A genotype refers to the genetic makeup of an organism, including its genes and alleles.

In essence: Natural selection doesn't "see" the genes themselves. It only sees how those genes express themselves in the form of phenotypes. For example, if a moth has a camouflage-colored phenotype that helps it avoid predators, it's more likely to survive and reproduce, regardless of its specific genotype.

The genotype provides the blueprint for the phenotype, but it's the phenotype that interacts with the environment and determines the organism's fitness.