| Lower Invertebrates | Higher Invertebrates |
| Generally small in size Simple body organisation Radial, bi-radial or no symmetry Germ Layers 2 or 3 (diplo / triploblastic) No Coelom or Pseudocoelom is present No separate mouth and anus No muscular gut Blood vascular system not well developed For example: Poriferans, Cnidarians | Generally larger in size Body organisation is complex Bilateral symmetry in most animals 3 germ layers (triploblastic organisms) True Coelom is present (Eucoelomates) Mouth and anus are separate True muscular gut is present Well developed blood vascular system For example: Arthropods, Echinoderms |