{ Characteristics }
Mollusks are soft-bodied animals that usually have an internal or external shell. All mollusks have a mantle.
Reproduction
Mollusks have one mean of reproducing. They reproduce sexually.
Mollusks can reproduce sexually through internal or external fertilization. Many gastropods and bivalves reproduce using external fertilization. They release enormous numbers of eggs and sperm into open water that fertilize and develop into free-swimming larvae. Cephalopods and certain gastropods reproduce using internal fertilization. Some mollusks are hermaphroditic, but usually fertilize eggs from another.
Examples of Mollusks
There are three major classes of mollusks: Gastropoda, Bivalvia, and Cephalopoda. The class Gastropoda includes pond snails, land slugs, sea butterflies, sea hares, limpets, and nudibranchs. They are shell-less or single-shelled mollusks that move by using a muscular foot located on the ventral side. The class Bivalvia include clams, oysters, mussels, and scallops. They have two shells that are held together by one or two powerful muscles. The class Cephalopoda includes octopi, squids, cuttlefishes, and nautiluses. They are typically soft-bodies mollusks in which the dead is attached to a single foot. The foot is divided into tentacles or arms.
Vocabulary
trochophore - free-swimming larva stage of an aquatic mollusk
foot - muscular part of a mollusk
mantle - thin layer of tissue that covers most of a mollusks body
shell - structure in mollusks made by glands in the mantle that secrete calcium carbonate
visceral mass - area beneath the mantle of a mollusk that contains the internal organs
radula - tongue-shaped structure used for feeding by snails and slugs
siphon - tubelike structure through which water enters and leaves a mollusk’s body
open circulatory system - system in which blood is not always contained within a network of blood vessels
Works Cited
http://science.plazza.us/wp-content/uploads/2011/05/mollusks.jpg
http://kentsimmons.uwinnipeg.ca/16cm05/1116/33-19-GastropodsCollage.jpg
http://cas.bellarmine.edu/tietjen/AnimalDiversity/bivalvia01.gif
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