Final answer:
A snail is a protostome bilateral animal due to its developmental characteristics and body plan. Protostomes, including arthropods, mollusks, and annelids, are named after the mouth developing first. The snail, as a member of the mollusk phylum and part of the Gastropoda class, exhibits bilateral symmetry.
Step-by-step explanation:
A snail is a protostome bilateral animal due to its developmental characteristics and body plan. Protostomes, including arthropods, mollusks, and annelids, are named after the mouth developing first. The snail, as a member of the mollusk phylum and part of the Gastropoda class, exhibits bilateral symmetry, meaning it can be divided into right and left sides that are mirror images of each other. Additionally, a key characteristic of some gastropods, including snails, is the embryonic development of torsion, where the body undergoes rotation during development. This process results in the loss of bilateral symmetry as the snail matures.