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Mollusks
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Phylum Mollusks - Molluscs include all the shelled creatures of the seashore, with the exception of the barnacles. Molluscs are abundant in the region between high and low tide and are a major feature of all rocky ocean shores. Molluscs form one of the largest groups in the animal kingdom, with more than 80,000 known species. Molluscs form a very well defined group and although their outside features may vary greatly in form and colour, their internal structure is constant.
It is believed that modern molluscs evolved from a creature similar to the one above. It had its gills, reproductive organs and excretory organs within its mantle cavity at the rear of the animal. Although there are numerous limpet-like fossils which are of this structure, only one species has been brought up from 5,000 metres near the coast of Mexico in the pacific Ocean. It was first captured in 1957.
There is one thing that all mollusks have in common: a foot. The foot is used for different purposes in each class, as you will see. They also have soft, fleshy bodies, a tongue-like organ called a radula, and usually a hard, external shell. See how the radula works. Picture of radula, and close-up picture of the radula (scary looking. Many are predatory on other invertebrates; anemones, sea urchins, other mollusks, and even fishes. Mollusks are the second largest invertebrate group (after the arthropods); some 50,000 valid living species have been described, plus another 35,000 fossil ones.
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