A set of three-nucleotide-long words that specify the amino acids for polypeptide chains. triploblastic Possessing three germ layers: the endoderm, mesoderm, and ectoderm. Most eumetazoa are triploblastic. trophic level[Gk. trophos, feeder] The division of species in an ecosystem on the basis of their main nutritional source. The trophic level that ultimately supports all others consists of autotrophs, or primary producers.