MOLLUSCA
Mollusks are one of the nine phyla and they are very successful. There are currently about 110,000 documented species that fall under Phylum Mollusca. Most mollusks live in the ocean or in an underwater habitat. Since most mollusks have shells, there is a vast fossil record of them. They are believed to have evolved from an ancestor of the flatworm about 650 million years ago. Mollusks have an open circulatory system. |