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Mollusks By: Kriel And Angelique
What are Mollusks? Mollusks are a group of creatures not a creature. They are a group of invertebrates such as slugs, snails, octopus, clams, oysters, cuttlefish, limpets, and squids and lots more. There are more than 100,000 different species of Mollusks alive today.
What do mollusks have in common? All mollusks are invertebrates. Most mollusks have a shell or a muscular foot to burrow and creep. All of the mollusks have soft bodies. The soft body includes lungs or gills for breathing. They also have digestive and reproduction part. Most mollusks have a soft, skin like organ covered with a hard outside shell.
Types of Mollusks Cephalopods Cephalopods are very active and have evolved out of their need for shells for protection from predators. In other words, they don’t need their shells anymore. Gastropods/Unipods They have just one shell that varies in size and shape from species to species. Snails belong to this group and are the only member of the mollusk family to be living in both land and water. Bivalves Bivalves are mollusks that are like clams and oysters. Smaller groups include tusk shells and chitons (oval mollusks with jointed plates)
Facts Mollusk can also be spelled Mollusc. Mollusks were some of the very first inhabitants of the earth. Some fossils of mollusks found in rocks date back to 500 million years ago. Mollusk fossils are usually very well preserved because of their hard shells. Most mollusks have a soft, skin like organ covered with a hard outside shell. Some mollusks live on land, like the slug and the snail, while others live in water, like the oyster, mussel, clam, squid and octopus.
How they reproduce Mollusks reproduce sexually. Slugs and snails are hermaphrodites (possessing both male and female organs), but they must still mate to fertilize their eggs. Most aquatic mollusks lay eggs that hatch into small, free-swimming larvae called veliger.
Even more facts The smallest type of mollusk is the Pythina clam. It is translucent and just about the size of a grain of rice. The biggest mollusk is the giant Tridacna clam. It has two four–feet long valves and may weigh up to 500 pounds. The shell of the giant Tridacna is, in fact, the largest sea shell known to man. Oysters and scallops are also bivalve mollusks.
How they eat Most mollusks have a rasping tongue called a radula, armed with tiny teeth. This scrapes tiny plants and animals off rocks or tears food into chunks. Bivalves, such as oysters and mussels, filter food particles from the water with their gills. Cephalopods such as octopuses and cuttlefish are stealthy hunters. Octopuses creep along the seabed or lie in wait for fish and crabs. They pounce on their prey, seize it with their suckered arms, and paralyze it with poisonous saliva.
About their shells Mollusk shells come in many shapes and sizes, but most have the same, simple function—providing somewhere to hide in times of danger. In land mollusks, the shell also helps to prevent the moist, soft-bodied creature from drying out. Mollusk shells are made of a chalky material called calcium carbonate. The shell has three layers for extra strength: a tough outer layer, a chalky middle layer, and a shiny inner layer, next to the animal’s skin. The shiny layer in some bivalve mollusks is known as mother-of-pearl.
More about shells A mollusk’s mantle (skin) releases liquid shell materials, which harden on contact with water or air. Gastropod shells grow from their outer edge. As the mollusk grows, its shell develops more whorls (single turns in a spiral shell) or chambers.
How they move Some move by pushing a big sole called a foot while the aquatic ones swim.(obviously) Snails used a protective jelly to protect their undersides from sharp things.
Time for something exciting!! The mollusk song
Bibliography http://www.wisegeek.com/what-is-a-mussel.htm http://en.wikipedia.org/wiki/Mollusca http://www.kidport.com/reflib/science/animals/Mollusks.htm http://www.infoplease.com/dk/encyclopedia/mollusks.html http://en.wikipedia.org/wiki/Valve_(mollusc)
