Animal Body Plans and Symmetry

Animals have a variety of body plans and levels of symmetry. Some animals have radial symmetry, which means that their body is arranged in a circular pattern around a central axis. Radially symmetrical animals include cnidarians such as jellyfish and sea anemones.

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Other animals have bilateral symmetry, which means that their body is divided into left and right halves that are mirror images of each other. Bilaterally symmetrical animals include most invertebrates and vertebrates.

Bilateral symmetry is further divided into two categories: cephalization and segmentation. Cephalization is the concentration of the head at the front end of the body. Cephalized animals have a head with specialized sense organs and a well-developed brain, which allows them to process and interpret sensory information. Segmentation is the division of the body into repeating units called segments. Segmented animals have a body that is divided into segments, each of which has a specific function.