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Symmetry, in biology, the repetition of the parts in an animal or plant in an orderly fashion. Specifically, symmetry refers to a correspondence of body parts, in size, shape, and relative position, on opposite sides of a dividing line or distributed around a central point or axis.
- The Editors of Encyclopaedia Britannica
Feb 13, 2017 · Bilateral symmetry refers to organisms with body shapes that are mirror images along a midline called the sagittal plane. The internal organs, however, are not necessarily distributed symmetrically.
Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symmetry down its centre, or a pine cone displays a clear symmetrical spiral pattern.
- Asymmetrical Symmetry: In some animals there are no body axis and no plane of symmetry, hence the animals are called asymmetrical. The amoeboid forms (e.g., Amoeba) and many sponges have irregular growth pattern of the body and cannot be divided into two equal halves (Fig.
- Spherical Symmetry: In spherical symmetry the shape of the body is spherical and lack any axis. The body can be divided into two identical halves in any plane that runs through the organism’s centre.
- Radial Symmetry: In radial symmetry the body can be divided into two roughly equal halves by any one of many vertical planes passing through the central axis (Fig.
- Biradial Symmetry: The body of animals which exhibits biradial symmetry, represents a combination of both radial and bilateral symmetry. The organs are arranged radially and the body can be divided into two by a mid-longitudinal plane.
Mar 13, 2021 · The two main types of symmetry are radial symmetry (in which body parts are arranged around a central axis) and bilateral symmetry (in which organisms can be divided into two near-identical halves along a single plane).
- Kate Latham
Aug 4, 2022 · Symmetry in biology is the balanced arrangement of body parts or shapes around a central point or axis. That is, the size, shape, and relative location on one side of a dividing line mirrors the size, shape, and relative location on the other side.
The type of symmetry is found in some sponges (Sycon), cnidarians (e.g. Hydra jelly), and echinoderms (e.g. star fish). When the body can be divided into two similar halves by one or two vertical planes only, the radial symmetry is called biradial symmetry.
