Degree to which an organism’s phenotype changes depending upon its current or past environment. Two organisms with the same genotype (e.g., identical twins) may have different phenotypes (e.g., one may be taller or heavier) if raised in different environments; those differences represent phenotypic plasticity. All organisms exhibit some degree of phenotypic plasticity (e.g., an animal that receives more food will generally be heavier than a genetically identical animal that receives less food), but sometimes phenotypic plasticity can be extreme (e.g., some fish become either male or female depending upon the temperatures they were exposed to as an egg). For more details, see our news story on the topic of phenotypic plasticity.