Search results
Results From The WOW.Com Content Network
Biological symmetry can be thought of as a balanced distribution of duplicate body parts or shapes within the body of an organism. Importantly, unlike in mathematics, symmetry in biology is always approximate. For example, plant leaves – while considered symmetrical – rarely match up exactly when folded in half.
Peloria or a peloric flower is the aberration in which a plant that normally produces zygomorphic flowers produces actinomorphic flowers instead. This aberration can be developmental, or it can have a genetic basis: the CYCLOIDEA gene controls floral symmetry. Peloric Antirrhinum plants have been produced by knocking out this gene. [5]
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]
Magnolia grandiflora, a spiraled flower.. Depending on the family considered, the pieces of the flower can be arranged on the receptacle in two different ways. In the case of the spiral arrangement, the parts are inserted consecutively and at different levels, describing a spiral on the axis in the same way as the leaves are inserted on the stem.
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.
Symmetry or arrangement may be described for the whole flower; in such case the corresponding symbol is usually placed at the beginning of the formula. It may be also outlined separately for different organs, placing it after their labels or numbers, or it may not be included in the formula at all.
Plant morphology "represents a study of the development, form, and structure of plants, and, by implication, an attempt to interpret these on the basis of similarity of plan and origin". [4] There are four major areas of investigation in plant morphology, and each overlaps with another field of the biological sciences.
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.