Why does natural selection act on phenotype no genotype or an organism?

Natrual selection does act on genotype. the reason is that the genotype affects the outcome of the phenotype. For other organisms to distinguish the difference between organisms, their has to be a phenotypic difference. For example, say brown bunnies survive better than white bunnies because they can hide better. The predator would easily spot the white bunny over the brown bunny. As a result natural selection acts out against the white bunny's phenotype because the predator can distinguish it better.