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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.
Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spirally arranged.
Homogamy is used in biology in four separate senses: Inbreeding can be referred to as homogamy. [1] Homogamy refers to the maturation of male and female reproductive organs (of plants) at the same time, which is also known as simultaneous or synchronous hermaphrodism and is the antonym of dichogamy. Many flowers appear to be homogamous but some ...
Animals mainly have bilateral or mirror symmetry, as do the leaves of plants and some flowers such as orchids. [30] Plants often have radial or rotational symmetry, as do many flowers and some groups of animals such as sea anemones. Fivefold symmetry is found in the echinoderms, the group that includes starfish, sea urchins, and sea lilies. [31]
Pelorism is the term, said to be first used by Charles Darwin, for the formation of 'peloric flowers' [1] which botanically is the abnormal production of radially symmetrical (actinomorphic) flowers in a species that usually produces bilaterally symmetrical (zygomorphic) flowers. [2] These flowers are spontaneous floral symmetry mutants.
All spermatophytes ("seed plants") possess flowers as defined here (in a broad sense), but the internal organization of the flower is very different in the two main groups of spermatophytes: living gymnosperms and angiosperms. Gymnosperms may possess flowers that are gathered in strobili, or the flower itself may be a strobilus of fertile leaves.
For example, flowers on eudicots (the largest group of dicots) most frequently have four or five petals while flowers on monocots have three or six petals, although there are many exceptions to this rule. [2] The petal whorl or corolla may be either radially or bilaterally symmetrical.
Macroscopic examples of chirality are found in the plant kingdom, the animal kingdom and all other groups of organisms. A simple example is the coiling direction of any climber plant, which can grow to form either a left- or right-handed helix. In anatomy, chirality is found in the imperfect mirror image symmetry of many kinds of animal bodies.