Radial symmetry

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Radial symmetry: coral skeletons ; Rotation axis perpendicular to the image plane, individual skeletons therefore also radially symmetrical in the image plane
Radial symmetry: jellyfish axis of rotation parallel to the image plane, symmetry therefore hardly visible

Radial symmetry or radial symmetry referred to in the Biology a special tri- or polydentate (polysymmetrische) symmetry shape with a plurality of radially extending through the longitudinal axis of symmetry planes, circular, in which identical parts are arranged in three dimensions around a central axis (rotation axis). Each of the planes of symmetry running through the central axis divides the body into similar or equal parts. This symmetry phenomenon can never assume the same perfection in living beings as in mathematical objects, but is still called symmetry and perceived as such.

Many cnidarians and most echinoderms are radially symmetric ( pentasymmetry ; five-fold). For example, B. the five-armed starfish in the rest position next to its axis of rotation five planes of symmetry, which each run through one of the arms and the axis of rotation. The coral skeletons shown have 24 such planes of symmetry. A distinction is made between the radial symmetry and the disymmetry (2 planes of symmetry; rib jellyfish ) and bilateral symmetry (one plane of symmetry; bilateria ).

In botany , radial symmetry often occurs in the structure of the flowers ; here are some examples of different numbers:

One also speaks of actinomorphic flowers that have two or more planes of symmetry (radial, radially symmetrical, radial, radial) flowers with more than two levels and disymmetrical (biradial) flowers with two levels ( bleeding heart , cruciferous ), and zygomorphic (bilateral) or dorsiventral flowers ( orchids , labiates ), which have only one plane of symmetry.

Individual evidence

  1. Theodor CH Cole: Dictionary of Biology. 4th edition, Springer, 2015, ISBN 978-3-642-55327-1 , p. 568.
  2. Lexicon of Biology: Radial Symmetry , accessed on January 6, 2017.
  3. ^ Theodor Rümpler : Illustrated gardening lexicon. 3rd edition, Parey, 1902, p. 805.