AP BIOLOGY

Detailed explanation-1: -Bilateral symmetry is the symmetrical arrangement of an organism or part of an organism along with a central axis so that the organism or part can be divided into two equal halves. Bilateral symmetry is an important anatomical feature of animals belonging to Phylum Platyhelminthes.

Detailed explanation-2: -The phylum Platyhelminthes, the flatworms, shows bilateral symmetry. In bilateral symmetry, you create two matching halves by drawing a line from the anterior (head) end of the organism to the posterior (tail) end.

Detailed explanation-3: -Organisms in phylum Cnidaria and Ctenophora are radially symmetrical. Bilateral symmetry is seen in phylum Platyhelminthes and all the following phyla.

Detailed explanation-4: -The Platyhelminthes are acoelomate flatworms: their bodies are solid between the outer surface and the cavity of the digestive system. Most flatworms have a gastrovascular cavity rather than a complete digestive system; the same cavity used to bring in food is used to expel waste materials.