 In order to evaluate these questions experimentally, researchers need to alter development through the manipulation of environmental variables and observe how a novel phenotype can be established within the existing plasticity of an organism (Kirschner and Gerhart 2005: ch. 5). This manipulation could allow for the identification of patterns of variation through the reliable replication of particular experimental alterations within different environmental regimes. However, without measuring variation across different environmental regimes, you cannot observe phenotypic plasticity. These measurements are required to document the degree of plasticity and its patterns for a particular trait, such as qualitatively distinct morphs. An evaluation of the significance of phenotypic plasticity for evolution requires answers to questions about where plasticity emerges, how molecular genetic mechanisms are involved in the plasticity, and what genotype-phenotype relations obtain.