Phenotypic variation refers to the observable traits or characteristics of an organism that result from the interaction between its genetic makeup and the environment. This variation can manifest as differences in physical appearance, behavior, or other observable traits within a species. Researchers study phenotypic variation to better understand how genetic and environmental factors influence the development and expression of traits in individuals, populations, and species. By examining phenotypic variation, scientists can gain insights into the mechanisms of evolution, adaptation, and the genetic basis of complex traits.