While you walk on the sea shore, you are sure to catch the sight of sea shells. Have you wondered what they are and how they ended up there?
Sea shells are nothing but the external skeletons of a class of marine organism called mollusks. These are soft bodied organisms with a hard outer shell. There are more than 40,000 species of mollusks most of which are confined to seas. Some are very dangerous while others are not. Most mollusks have shells, well defined foot and a fleshy mantle that encloses the animal’s body. While some are well-known for their shells others may not have shells at all. The shells made of calcium are hard and they act as a protection against predators, storms and strong currents.
The eight plated chitons, tentacled tusk shells, squid, oysters, limpets and octopuses are also mollusks. The two well known categories of mollusks are single shelled or univalves (snail, conch) and those with bivalves (clams and oysters). Pounded by waves, mollusks living on sea shore lead a very uncertain life. Most of them stay buried in the muddy or sandy bottom and are active only in the dark. Sometimes the top shell is easily dislodged and rolled about by the tides. Also when these organisms die, their shells are washed up onto the shore.
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