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Radial symmetry is especially suitable for sessile animals such as the sea anemone, floating animals such as jellyfish, and slow moving organisms such as starfish; whereas bilateral symmetry favours locomotion by generating a streamlined body. Many flowers are also radially symmetric, or "actinomorphic".
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.
The flowers called actinomorphics, radiate or polysymmetric have radial symmetry, as is the case of Tulipa gesneriana or Linum usitatissimum . In contrast, monosymmetrica l, dorsiventral or zygomorphic flowers have bilateral symmetry and the evolution of their shape is related to the need to attract and guide pollinators to them, as for example ...
Actinomorphic – having a radial symmetry, as in regular flowers. Actinomorphy – when the flower parts are arranged with radial symmetry. Radial – symmetric when bisected through any angle (circular) Unisexual – Zygomorphic – one axis of symmetry running down the middle of the flower so the right and left halves reflect each other.
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]
Flowering plants underwent a major diversification after this period. Darwin saw this as an "abominable mystery" in a letter to Joseph Hooker in 1879. The earliest flowers were principally actinomorphic or having radial symmetry with multiple axes of symmetry. These evolved flowers have bilateral symmetry or zygomorphy.
A plant which completes its life cycle (i.e. germinates, reproduces, and dies) within two years or growing seasons. Biennial plants usually form a basal rosette of leaves in the first year and then flower and fruit in the second year. bifid Forked; cut in two for about half its length. Compare trifid. bifoliate
Plants and sessile (attached) animals such as sea anemones often have radial or rotational symmetry, which suits them because food or threats may arrive from any direction. Fivefold symmetry is found in the echinoderms , the group that includes starfish , sea urchins , and sea lilies .