Most animals exhibit bilateral symmetry during their development, which means their bodies can be divided into two mirror-image halves along a single plane. This symmetry allows for more streamlined movement and organization of body structures, which is advantageous for complex organisms. Bilateral symmetry is characteristic of many animal groups, including arthropods, vertebrates, and mollusks. In contrast, other forms of symmetry, like radial symmetry, are common in simpler organisms, such as jellyfish, showcasing the diversity of body plans in the animal kingdom.