1. Types of Symmetry and Animal Bodies

2.  Symmetry is the arrangement of body parts around a central plane or axis  Asymmetry : occurs when the body can't be divided into similar sections (sponges)  Radial symmetry: occurs when similar body parts are arranged around a central point like spokes on a wheel (echinoderms)  Bilateral symmetry: occurs when animals can be divided into equal halves along a single plane

4. Types of Symmetry and Animal Bodies  Most animals with radial symmetry are sessile (attached) or sedentary (move very little).  In animals with bilateral symmetry the right & left sides are mirror images of one another.  Animals with bilateral symmetry are more complex, usually motile and are animals such as worms, arthropods, and all vertebrates.  Animals with bilateral symmetry show cephalization which means that they have a head with sensory organs concentrated there.

6.  Dorsal: is the back or upper surface  Ventral: is the belly or lower surface  Anterior: head or front end  Posterior: is the tail or hind end opposite the head  Oral surface in echinoderms is where the mouth is located (underside)  Aboral surface in echinoderms is the surface opposite the mouth (top side) Body Areas: