Classification: Mollusca are classified as Protostomia. Protostomia are animals with bilateral symmetry and three germ layers.
For higher classification, Mollusca are known as Lophotrochozoa. Lophotrochozoa has ciliated tentacles in the mouth and both sides of the worm is bilaterally symmetrical. For lower classification, Mollusca falls under the category of Bivalvia, Pleistomollusca, and Chiton. All these species are worms with shells that have two hinged parts. Diversity: Mollusca are different from other phylums because they consist of three parts. The Mollusca have a foot, a visceral mass, and a mantle. The Mollusca secretes mucus from the bottom of its foot which lubricates the underlying surface. The Mantle covers the visceral mass and contains glands that secrete a hard shell. The visceral mass contains the digestive system, the heart, and other organs. The circulatory system in the Mollusca is open and it uses a single pair of gills to breathe. Mollusca transport oxygen throughout their bodies differently than other invertebrate phylums. They use a molecule called haemocyanin, a copper-based molecule while other vertebrates use haemoglobin, an iron-based molecule. Haemocyanin is less efficient in transporting oxygen causing mollusca to tire very easily. Life History: Mollusca has evolved from a segmented worm-like animals similar to flatworms. Mollusca begin their life as ciliated, free swimming larvae to later develop into adult form. Mollusca reproduce through sexual reproduction with male containing sperm and female containing eggs. The male injects sperm into the female with an egg producing an offspring. The mollusca lay eggs that hatch with veliger (free swimming larvae). Mollusca have a rasping tongue called a radula, armed with tiny teeth. With the radula the Mollusca is able to scrape tiny plants and animals off rocks, devouring or tearing the food into chunks. Ecological Roles: Mollusca are vital to keeping the ecosystem healthy. Mollusca are food for many species such as birds and small mammals. Mollusca are important because they recycle forest nutrients. They also recycle plane and animal waste keeping the water clean and healthy. Mollusca keep the water and natural environment clean from waste and toxins. Human Impacts: Mollusca aren't just food for animals but for humans as well. Humans use snails at bait for fishing and medical purposes. Some use Mollusca to host parasitic flatworms. Works Cited http://www.britannica.com/EBchecked/topic/388398/mollusk http://www.biology-questions-and-answers.com/mollusca.html http://animals.about.com/od/molluscs/p/molluscs.htm |