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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.
In biology, the notion of symmetry is also used as in physics, that is to say to describe the properties of the objects studied, including their interactions. A remarkable property of biological evolution is the changes of symmetry corresponding to the appearance of new parts and dynamics.
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.
Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachiopods, a stalk-like pedicle projects from an opening near the hinge of one of the valves, known as the pedicle or ventral valve.
Irregular or unequal; lacking any plane of symmetry; e.g. flowers of Canna. attenuate Narrowing gradually. See also Leaf shape. auricle An ear-shaped lobe, particularly a small, roundish, lateral appendage of a leaf or leaf-like organ. auriculate Attached at the base with ear-shaped appendages (auricle s). See also Leaf shape. autogamous
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.
A symmetry plane parallel with the principal axis is dubbed vertical (σ v) and one perpendicular to it horizontal (σ h). A third type of symmetry plane exists: If a vertical symmetry plane additionally bisects the angle between two 2-fold rotation axes perpendicular to the principal axis, the plane is dubbed dihedral (σ d). A symmetry plane ...
Evolutionary developmental biology – Comparison of organism developmental processes; Definition of Phylum based on body plan – High level taxonomic rank for organisms sharing a similar body plan; Ediacaran biota – Life of the Ediacaran period; Macroevolution – Evolution on a scale at or above the level of species