Youtor
Sea Shells
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A sea shell is a hard, protective outer layer created by an animal that lives in the sea. • The shell is part of the body of the animal. • Empty seashells are often found washed up on beaches by beachcombers. • The term seashell usually refers to the exoskeleton of an invertebrate which is an animal without a backbone. • Most shells that are found on beaches are the shells of marine mollusks, partly because many of these shells endure better than other seashells. • Seashells have been used by humans for many different purposes throughout history and pre-history. • Seashells are commonly found in beach drift, which is deposited along strandlines on beaches by the waves and the tides. • Shells are very often washed up onto a beach empty and clean, the animal having already died, and the soft parts having rotted away or having been eaten by either predators or scavengers. • Bivalves are often the most common seashells that wash up on large sandy beaches or in sheltered lagoons. • They can sometimes be extremely numerous. Very often the two valves become separated. • There are more than 15,000 species of bivalves that live in both marine and freshwater. • Examples of bivalves include clams, scallops, mussels, and oysters. • The majority of bivalves consist of two identical shells that are held together by a flexible hinge. • The animal's body is held protectively inside these two shells. • Bivalves that do not have two shells either have one shell or they lack a shell altogether. • The shells are made of calcium carbonate and are formed in layers by secretions from the mantle. • Bivalves are mostly filter feeders; through their gills, they draw in water, in which is trapped tiny food particles. • Some bivalves have eyes and an open circulatory system. • Bivalves are used all over the world as food and as a source of pearls. • Seashells have been used as a medium of exchange in various places, including many Indian Ocean and Pacific Ocean islands, also in North America, Africa and the Caribbean. • Seashells have often been used as tools, because of their strength and the variety of their shapes. • Giant clams have been used as bowls, and when big enough, even as bathtubs and baptismal fonts. • Many different species of bivalves have been used as scrapers, blades, clasps, and other such tools, due to their shape. • Some marine gastropods have been used for oil lamps, the oil being poured in the aperture of the shell, and the siphonal canal serving as a holder for the wick. • Because seashells are in some areas a readily available bulk source of calcium carbonate, shells such as oyster shells are sometimes used as soil conditioners in horticulture. • The shells are broken or ground into small pieces in order to have the desired effect of raising the pH and increasing the calcium content in the soil. • For more videos, photos and blog posts like this please visit http://www.wholesomeday.com • Twitter: / wholesomeday • Tumblr: / wholesomeday • Pinterest: / wholesomed • Facebook: / wholesomeday
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