Dentist specialties are recognized in those areas where advanced knowledge and skills are essential to maintain or restore oral health. The list of recognized dental specialties differs from country to country.
In contrast, radially symmetrical animals like jellyfish have a topside and a downside, but no identifiable front or back. The bilateria are a major group of animals, including the majority of phyla but not sponges, cnidarians, placozoans and ctenophores. For the most part, bilateral embryos are triploblastic, having three germ layers: endoderm, mesoderm, and ectoderm.
Phylum Platyhelminthes (the flatworms) ~1300 species ie: Planarians, Tapeworms, Flukes Some are free living and some are parasitic. Soft, flattened worms with tissues and internal organ systems.The simplest animals to have 3 germ layers, bilateral symmetry, and cephalization.Bilaterally symmetrical: Most primitive bilaterally symmetrical organism Acoelomate: but no coelom Coelom-fluid filled body cavity, lined with tissue derived from mesoderm.oft, flattened worms with tissues and internal organ systems. The simplest animals to have 3 germ layers, bilateral symmetry, and cephalization. Bilaterally symmetrical: Most primitive bilaterally symmetrical organism Acoelomate: but no coelom Coelom-fluid filled body cavity, lined with tissue derived from mesoderm.