Which term refers to a body composed of two germ layers?

The term that refers to a body composed of two germ layers is "didermic." In the context of embryonic development, organisms can be categorized based on the number of germ layers that develop during the early stages of embryogenesis.

Didermic organisms, also known as diploblastic organisms, develop two primary germ layers: the ectoderm and the endoderm. This structural organization is significant because these layers give rise to various tissues and organs. For example, the ectoderm contributes to the formation of the skin and nervous system, while the endoderm forms the lining of the digestive tract and associated organs.

In contrast, the other terms refer to different configurations of germ layers. Monodermic refers to organisms with only one germ layer, which is uncommon and primarily seen in very simple organisms. Tridermic pertains to organisms with three germ layers (ectoderm, mesoderm, and endoderm), which includes most higher animals, including humans. Polydynamic isn't a standard biological term related to germ layers. Thus, didermic clearly identifies the specific evolution and organization of two-layered biological structures.