GENERAL HISTOLOGY

Detailed explanation-1: -symmetry, in biology, the repetition of the parts in an animal or plant in an orderly fashion. Specifically, symmetry refers to a correspondence of body parts, in size, shape, and relative position, on opposite sides of a dividing line or distributed around a central point or axis.

Detailed explanation-2: -Bilateral symmetry: It is an arrangement of parts which are distributed in equal halves about a vertical plane or the unique plane running from head (top) to tail (bottom). Bilateral symmetry has the property of being divisible in equal symmetrical halves on both the sides along one plane. For example, humans.

Detailed explanation-3: -Animals have been traditionally classified according to two characteristics: body plan and developmental pathway. The major feature of the body plan is its symmetry: how the body parts are distributed along the major body axis. Symmetrical animals can be divided into roughly equivalent halves along at least one axis.

Detailed explanation-4: -Animals in the phylum Echinodermata (such as sea stars, sand dollars, and sea urchins) display radial symmetry as adults, but their larval stages exhibit bilateral symmetry. This is termed secondary radial symmetry.

Detailed explanation-5: -At a very basic level of classification, true animals can be largely divided into three groups based on the type of symmetry of their body plan: radially symmetrical, bilaterally symmetrical, and asymmetrical.