Final answer:
Bilaterally symmetrical animals have a body plan with concentrated sense organs at the anterior end, enhancing sensory perception and allowing swift detection of environmental stimuli, which is advantageous for survival.
Step-by-step explanation:
Most bilaterally symmetrical animals have an anterior end where most of the sense organs are located. This body plan provides the advantage of enhancing sensory perception, as it presents a clear directionality with the anterior end leading. Bilaterally symmetrical animals, like a butterfly, crab, or human, have a 'head' and 'tail' (anterior vs. posterior), front and back (dorsal vs. ventral), and right and left sides. This arrangement enables cephalization, the formation of a concentration of nervous tissues and sensory organs at the animal's front, which encounters the environment first during forward motion.
This organization is critical for survival, as it allows for improved environmental interaction and responsiveness. For instance, as an animal moves forward, sensory inputs such as sights, sounds, and smells are encountered with the anterior end first. Having sense organs located here allows the animal to swiftly detect food, predators, and mates, facilitating better decision-making and reactions.