ABSTRACT
Second, even if such interaction is reduced to its simplest expression, one in which a trait develops from the interplay of genotype and the external environment, the number of potential outcomes can be considerably large. Identical twins are genetically identical but, otherwise, organisms are genetically unique because of the independent assortment of alleles in meiosis. Something similar also holds for environments. To the extent that environments are defined by the organism, they are also unique. Additionally, the interaction of genotypes and environments implies that even when one of them is held constant, variation in the other term can lead to different phenotypes.
