Phylum Mollusca Essay

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Phylum Mollusca Phylum Mollusca consists of soft bodied animals that usually have a shell. There are around eighty thousand species of Mollusca. With Anthropods being the largest phylum, the amount of mollusks species puts Phylum Mollusca as the second largest Phylum. Mollusks are an important food source and move by pseudopods, or false feet. Each mollusk has a mantle. The mantle is the tissue covering the internal organs and also functions to secrete the shell, if the mollusk has a shell. Mollusks have circulatory, digestive, excretory, and gas exchange systems. They also reproduce sexually and are hermaphrodites, which means they are of both sexes. The body of a mollusk is divided into three different parts: the head, the foot, and the visceral mass or internal organs. There are three classes of Mollusca. Gastropods and Pelecypods are both shelled classes while Cephalopods are not. Gastropods are the largest class in Phylum Mollusca. They are univalves, meaning they only have one shell. Some examples of Gastropods are snails and abalone. Gastropods have a mouth structure called a radula. This radula is like a toothed tongue. Gastropods also have an operculum, a trap door that covers the opening of the shell. Some are predators, feeding off of small marine fish and some are herbivores, feeding on algae, plant material, and bacteria. There are about six hundred and ten families of gastropods. Of that six hundred and ten, about two hundred, or thirty percent, of those families are extinct and can only be found in fossil records. Gastropods are the most highly diversified class in Phylum Mollusca. The significant varying behavior, feeding, anatomy, and reproductive adaptations of the different groups of Gastropods make it hard to state many generalizations of all Gastropods. Pelecypods consist of bivalves, marine animals with two shells. Some examples of

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