Why is bilateral symmetry useful for animals that move actively?

Bilateral symmetry is highly advantageous for animals that move actively because it facilitates efficient, directed movement through an environment. This body plan allows for the concentration of sensory organs at the anterior end, or head, of the animal—a process known as cephalization. By placing sensory apparatus at the forward-moving end, an animal can better perceive and respond to its surroundings while navigating.12

Furthermore, bilateral symmetry allows for the efficient arrangement of locomotor structures, such as limbs and muscle layers, along both sides of the body. This balanced distribution supports coordinated movement. In these animals, the diffuse nerve net found in simpler organisms typically evolves into organized tracts or bundles that run from the anterior brain to innervate these locomotor structures, enabling precise control during active pursuit of food.1