In biology, bilateral symmetry is a characteristic of multicellular organisms, particularly animals. A bilaterally symmetric, or bilaterian, organism is one that is symmetric about a plane running from its frontal end to its caudal end (head to tail), and has nearly identical right and left halves. Main articles: Life All organisms (viruses not included) consist of cells, which in turn, are based on a common carbon-based biochemistry. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Subregnum Bilateria  Acoelomorpha  Orthonectida  Rhombozoa  Myxozoa  Superphylum Deuterostomia     Chordata (vertebrates, etc. ... Symmetry is a characteristic of geometrical shapes, equations and other objects; we say that such an object is symmetric with respect to a given operation if this operation, when applied to the object, does not appear to change it. ...

Most animals are bilaterally symmetric, including humans (see also facial symmetry). The exceptions are the porifera (sponges) (no symmetry); and the choanoflagellata, placozoa, cnidaria (jellyfish) and the ctenophores, which exhibit radial symmetry. Bilateral animals belongs to a group called Bilateralia. The oldest known bilateral animal is called Vernanimalcula. Facial symmetry is a determinant of the health, physical attractiveness and beauty of a person. ... The sponge, in the phylum Porifera, is a very primitive and specialized animal. ... Classes Calcarea Hexactinellida Demospongiae Sclerospongiae The sponges or poriferans (from Latin porus pore and ferre to bear) are animals of the phylum Porifera. ... Composed of only about 150 species, the Choanoflagellata are not a diverse group of protists. ... Trichoplax adhaerens is a simple balloon-like marine animal with a body cavity filled with pressurized fluid. ... Classes Anthozoa - Corals and sea anemones Cubozoa - Sea wasps or box jellyfish Hydrozoa - Hydroids, hydra-like animals Scyphozoa - Jellyfish Cnidaria (from New Latin cnida nematocyst, fr. ... Orders Stauromedusae Coronatae Semaeostomae - Disc jellyfish Rhizostomae Jellyfish (also called jellies or sea jellies as they are not true fish) are animals that belong to Phylum Cnidaria, included in the class Scyphozoa (from Greek skyphos cup and zoon animal). The name jellyfish is also sometimes used for the related classes... Classes Tentaculata Nuda Ctenophores are jellyfish-like animals commonly called comb jellies, sea gooseberries, sea walnuts, or Venus girdles. ... In biology, radial symmetry is a property of some multicellular organisms. ... The oldest known examples of a bilaterian, bilateral animals. ...

Other animals which appear to possess radial symmetry have a body plan which is basically bilaterally symmetric. The echinoderms exhibit pentaradial symmetry or pentamerism but this is a secondary characteristic - echinoderm larvae are bilaterally symmetric, as are echinoderm ancestors. Some sea urchins (class Echinoidea) have further modified their radial symmetry to become bilaterally symmetric again. In biology, radial symmetry is a property of some multicellular organisms. ... Classes Asteroidea Concentricycloidea Crinoidea Echinoidea Holothuroidea Ophiuroidea Echinoderms (Echinodermata) is a phylum of marine animals found in the ocean at all depths. ... In biology, pentamerism, also known as pentaradial symmetry, is a unique body symmetry exhibited primarily by starfish. ... In biology, pentamerism, also known as pentaradial symmetry, is a unique body symmetry exhibited primarily by starfish. ... Subclasses Euechinoidea Superorder Atelostomata Order Cassiduloida Order Spatangoida (heart urchins) Superorder Diadematacea Order Diadematoida Order Echinothurioida Order Pedinoida Superorder Echinacea Order Arbacioida Order Echinoida Order Phymosomatoida Order Salenioida Order Temnopleuroida Superorder Gnathostomata Order Clypeasteroida (sand dollars) Order Holectypoida Perischoechinoidea Order Cidaroida (pencil urchins) Slate pencil urchin (cidaroid) Group of black... Slate pencil urchin (cidaroid) Group of black, long-spined Caribbean sea urchins, Diadema antillarum (Philippi) Sea urchin roe. ... In biology, radial symmetry is a property of some multicellular organisms. ...

Adult flatfish have both eyes on the same side of their body, but their body plan is still bilaterally symmetric, if a little twisted. Families Suborder Psettodoidei     Psettodoidae Suborder Pleuronectoidei     Citharidae     Scophthalmidae     Bothidae (lefteye flounders)     Pleuronectidae (righteye flounders)     Paralichthyidae     Achiropsettidae (southern flounders)     Samaridae Suborder Soleoidei     Soleidae (soles)     Achiridae (American soles)     Cynoglossidae (tonguefishes) The flatfish are an order (Pleuronectiformes) of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. ...