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Reynold Berge ∙
Celiaphlatus and forward movement. There is a few advantages of the bilateral symmetry. Some of the advantages are food, movement and animals.
Medusa
memes
sponges
Chelicerates (crabs, Pycnogonida, and Mercostonata) are arthropods that lack jaws.
platyhelminthes
sea stars
A leech is not a mollusk.
Altruism is a form of self-sacrificing behavior.