Mussels are molluscs and are related to water snails. Because their shells are divided into two halves, they are called bivaldes. The shell protects the soft body of the animal. A powerful foot enables the animal to...

Parasites are animals that live at the expense of other animals. They rob the host animal of nourishment and often cause it to become sick. However, in other types of relationships, different animals can help one anothe...