The genotype–phenotype distinction is drawn in genetics. "Genotype" is an organism's full hereditary information. "Phenotype" is an organism's actual observed properties, such as morphology, development, or behavior. This distinction is fundamental in the study of inheritance of traits and their evolution. Overview The terms "genotype" and "phenotype" were created by Wilhelm Johannsen in 1911, although the meaning of the terms and the significance of the distinction have evolved since they were introduced. It is the organism's physical properties that directly determine its chances of survival and reproductive output, but the inheritance of physical properties is dependent on the inheritance of genes. Therefore, understanding the theory of evolution via natural selection requires understanding the genotype–phenotype distinction. The genes contribute to a trait, and the phenotype is the observable expression of the genes (and therefore the genotype that affects the trait). If a white mouse had recessive genes that caused the genes responsible for color to be inactive, its genotype would be responsible for its phenotype (the white color). The mapping of a set of genotypes to a set of phenotypes is sometimes referred to as the genotype–phenotype map. An organism's genotype is a major (the largest by far for morphology) influencing factor in the development of its phenotype, but it is not the only one. Even two organisms with identical genotypes normally differ in their phenotypes. One experiences this in everyday life with monozygous (i.e. identical) twins. Identical twins share the same genotype, since their genomes are identical; but they never have the same phenotype, although their phenotypes may be very similar. This is apparent in the fact that close relations can always tell them apart, even though others might not be able to see the subtle differences. Further, identical twins can be distinguished by their fingerprints, which are never completely identical. Phenotypic plasticity The concept of phenotypic plasticity defines the degree to which an organism's phenotype is determined by its genotype. A high level of plasticity means that environmental factors have a strong influence on the particular phenotype that develops. If there is little plasticity, the phenotype of an organism can be reliably predicted from knowledge of the genotype, regardless of environmental peculiarities during development. An example of high plasticity can be observed in larval newts1: when these larvae sense the presence of predators such as dragonflies, they develop larger heads and tails relative to their body size and display