Final answer:
Bilateral symmetry enables animals to have organized nervous systems with distinct head (anterior) and tail (posterior) ends, aiding in streamlined and directional movement. This form of symmetry allows for the efficient placement of sensory and locomotory organs, which is essential for active life and complex behaviors.
Step-by-step explanation:
Bilateral symmetry is a form of symmetry in which an animal can be divided through a midsagittal plane, resulting in two halves that are mirror images. This symmetry is significant because it enables animals to possess a head and a tail (anterior vs. posterior), a front and a back (dorsal vs. ventral), and distinct right and left sides. Bilateral symmetry has led to the phenomenon of cephalization, the concentration of nerve tissue at the anterior or head end of an organism, which is crucial for the development of an organized nervous system.
Cephalization and the resulting bilateral body plan allow for streamlined movement and controlled, directional mobility, which are advantageous for seeking resources and engaging in predator-prey interactions. Unlike the more stationary lifestyle suited to radial symmetry, bilateral symmetry is associated with higher levels of activity and mobility. It enables efficient placement of locomotory and sensory organs, aiding in controlled movements and specialized functions that meet an animal's lifestyle demands.
Animals exhibiting bilateral symmetry tend to have a fusiform shape, particularly in aquatic environments, which reduces drag and allows for higher speeds when swimming.