The phenotype is the observable total physical appearance or selected expressed traits of the genotype in an individual organism or group of organisms effected by environmental influences. The traits or outward expressions of an organisms genetic makeup include eye color, skin color, hair color, weight or feeding habits, etc.
It is quite hard to actually observe the genotype of an organism compared rather to its phenotype from which classical genetics was able to deduce gene function. Phenotypes rely on an underlying heritable mechanism of genetic variation through what is called allelomorphs or alleles. This enables a fundamental view into mutation-selection change within evolution theory. Creationism relies upon those two mechanisms functioning within nature as a driving force of diversity as well, but it is of limited capacity that creationism predicts.
A total threshold of the triggered change in the organism from the immediate environment can as well be viewed by scientists and through that direct human observational science the structure of the organism's homology in question is isolated. This in turn isolates further down to the molecular level, the genes that manifest such structures (i.e. antenna, limbs) or behaviors (i.e. eating or mating habits) can be studied and deciphered showing relationships and scale of the genes. These isolated genes, as one study has indicated within the female Drosophila melanogaster, are responsible for the abdominal pigmentation changes being triggered by environmental fluctuation in temperature. 
When the environment triggers the already established phenotype present to instantly change it is called phenotypic plasticity. However regardless of the trigger mechanism it is thus concluded that the genes in question or the phenotype are a region isolated from the total genotype usually for study and experimentation.
- Phenotypic Plasticity in Drosophila Pigmentation Caused by Temperature Sensitivity of a Chromatin Regulator Network by Jean-Michel Gibert, Frédérique Peronnet, and Christian Schlötterer. PLoS Genet. 2007 February; 3(2): e30.