The Radial symmetry reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Radial symmetry

In biology, radial symmetry is a characteristic that is used to help classify multicellular organisms. It refers to the fact that it's possible to make any cut through the center of the organism, with the plane of the cut going from the top to the bottom (dorsal to ventral), and result in roughly equal halves in terms of organs and/or body parts. (Multi-layered circular pies 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. Jellyfish and ctenophores are the only animals with true radial symmetry; echinoderms have partial radial symmetry.

See also: bilateral symmetry, pentamerism

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