Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Diploblasts are animals that develop from two primary germ layers: the ectoderm and the endoderm. They lack a mesoderm, which is present in more complex organisms called triploblasts.
5 Must Know Facts For Your Next Test
Diploblasts include phyla such as Cnidaria (jellyfish, corals) and Ctenophora (comb jellies).
They have radial symmetry, meaning their body plan is arranged around a central axis.
The ectoderm forms the outer layer of cells, while the endoderm forms the inner lining of the gut.
Diploblastic animals do not possess true muscles derived from mesoderm; instead, they have simple muscle-like cells.
They typically exhibit simple tissue organization and lack complex organs found in triploblastic organisms.
Review Questions
Related terms
Triploblasts: Animals that develop from three primary germ layers: ectoderm, mesoderm, and endoderm.
Germ Layers: Primary layers of cells in embryonic development that give rise to all tissues and organs.
Radial Symmetry: A body plan in which any longitudinal cut through the organism's central axis results in identical halves.