Depending on environmental conditions, a locust can become either of two distinct phenotypes

The phenotype refers to the observable features of an organism; including the morphology, physiology, development and behaviour. The phenotype is the result of the organism’s genotype and environmental factors. Even individuals with the same genotype (e.g. identical twins) will not have the same phenotype if raised in different environments. Natural selection can only act upon the phenotype of an organism.

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Glossary of Galapagos