EVERYDAY SCIENCE

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: -Most animals are bilaterally symmetrical with a line of symmetry dividing their body into left and right sides along with a “head” and “tail” in addition to a top and bottom. Only sponges (phylum Porifera) have asymmetrical body plans.

Detailed explanation-3: -The literal definition of symmetry is balanced proportions. At a basic level of classification, true animals can be broadly classified into three groups based on the type of symmetry in their body. These three groups of organisms are radially symmetrical, bilaterally symmetrical, and asymmetrical.

Detailed explanation-4: -Bilateral symmetry is observed in animals which are cephalized, which means they have heads or head-like structures. Organisms which display bilateral symmetry have near identical left and right halves. Radial symmetry refers to symmetry where the organism may be cut multiple times on a median plan.

Detailed explanation-5: -Having bilaterally symmetrical bodies (the same on both sides along an axis) permit them to propel forward in a straight line. In evolutionary history, animals that moved quickly and efficiently from point A to point B would have been more successful and selected for than those who were ineffective at locomoting.