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Symmetry

Vitruvian Man by Leonardo da Vinci

Symmetry refers to balance. In nature there are four kinds of symmetry:

Bilateral Symmetry: has only one plane along the longitudinal axis that will produce identical halves. All vertebrates exhibit bilateral symmetry.
Radial Symmetry: exhibits a circular body plan with a circular arrangement around a central axis. The animal can be cut through the central axis in more than one plane to produce identical halves. Jellyfish, Anemone, and starfish exhibit radial symmetry.
Spherical Symmetry: exhibits a spherical body plan and can be divided into identical halves through any plane which passes through the center.
Asymmetrical: has no pattern of symmetry. Sponges are asymmetrical.