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All bilaterians have some asymmetrical features; for example, the human heart and liver are positioned asymmetrically despite the body having external bilateral symmetry. [14] The bilateral symmetry of bilaterians is a complex trait which develops due to the expression of many genes. The bilateria have two axes of polarity. The first is an ...
A gynandromorph can have bilateral symmetry—one side female and one side male. [24] Alternatively, the distribution of male and female tissue can be more haphazard. Bilateral gynandromorphy arises very early in development, typically when the organism has between 8 and 64 cells. [25] Later stages produce a more random pattern. [citation needed]
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.
Therefore, the theory assumes that bilateral symmetry is more primitive than radial symmetry. However, current biological evidence shows that the most primitive forms of metazoans show radial symmetry, and thus radially symmetrical animals like cnidaria cannot be derived from bilateral flatworms.
A foxglove with a peloric flower. (Digitalis purpurea 'monstrosa')A peloric foxglove (Digitalis purpurea) flowerPelorism 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]
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
A Phalaenopsis flower. Orchids are easily distinguished from other plants, as they share some very evident derived characteristics or synapomorphies.Among these are: bilateral symmetry of the flower (zygomorphism), many resupinate flowers, a nearly always highly modified petal (labellum), fused stamens and carpels, and extremely small seeds.
Bilateria (/ ˌ b aɪ l ə ˈ t ɪər i ə /) [5] is a large clade of animals characterised by bilateral symmetry during embryonic development.This means their body plans are laid around a longitudinal axis with a front (or "head") and a rear (or "tail") end, as well as a left–right–symmetrical belly and back surface.