Radial symmetry
|
|
In biology, radial symmetry is a property of some multicellular organisms. Any cut through the center of a radially symmetric organism, with the plane of the cut going from the top to the bottom (dorsal to ventral), results in roughly equal halves in terms of organs and body parts. For example, wedding cakes exhibit radial symmetry.
Organisms with radial symmetry only have a single orientation: dorsal-ventral (or anterior-posterior, there is no differentiation). Organisms with bilateral symmetry, on the other hand, have two orientations: dorsal-ventral, as well as anterior-posterior. Cnidaria and ctenophores are the only animals with true radial symmetry; echinoderms have partial radial symmetry. Starfish possess a variant of radial symmetry in which orientations of 72 degree rotation are considered equivalent; this is known as pentamerism.