which part of the mollusk body contains organs?

Identifies the structures found in mollusks and how these structures function. Have you ever been to the ocean or eaten seafood? [78] Scientists disagree about this: Giribet and colleagues concluded, in 2006, the repetition of gills and of the foot's retractor muscles were later developments,[12] while in 2007, Sigwart concluded the ancestral mollusc was metameric, and it had a foot used for creeping and a "shell" that was mineralized. [13], The mantle edge secretes a shell (secondarily absent in a number of taxonomic groups, such as the nudibranchs[13]) that consists of mainly chitin and conchiolin (a protein hardened with calcium carbonate),[16][28] except the outermost layer, which in almost all cases is all conchiolin (see periostracum). Squid and octopi are in this group. About 42% of recorded extinctions since the year 1500 are of molluscs, consisting almost entirely of nonmarine species. Nearly all fish spawn, as do crustaceans (such as crabs and shrimp), mollusks (such as oysters), squid, and echinoderms (such as sea urchins and sea cucumbers). Mollusk - Organ systems | Britannica Learn about the digestive systems and radula of phylum . [15]:300343,367403 The best natural pearls are produced by marine pearl oysters, Pinctada margaritifera and Pinctada mertensi, which live in the tropical and subtropical waters of the Pacific Ocean. The initial velocity of the proton has a magnitude v0v_0v0 and is directed at an angle \alpha below the horizontal. They are particularly useful since they are sessile so that they are representative of the environment where they are sampled or placed. Damage to the mantle can interfere with shell formation. The primary function of protein is to act as a building block for the body. Articles from Britannica Encyclopedias for elementary and high school students. 31 (34): 144..), Opinions vary about the number of classes of molluscs; for example, the table below shows seven living classes,[19] and two extinct ones. The mollusks stomach acts as a kind of sorting facility, where desirable nutrients are sent to be digested, and undesirable materials are sent to be excreted without being digested first. [23] The giant squid, which until recently had not been observed alive in its adult form,[24] is one of the largest invertebrates, but a recently caught specimen of the colossal squid, 10m (33ft) long and weighing 500kg (1,100lb), may have overtaken it. They include snails, slugs and other gastropods; clams and other bivalves; squids and other cephalopods; and other lesser-known but similarly distinctive subgroups. Before the mucus string reaches the prostyle, the acidity of the stomach makes the mucus less sticky and frees particles from it. [15]:Front endpaper About 200,000living species in total are estimated,[1][21] and 70,000 fossil species,[14] although the total number of mollusc species ever to have existed, whether or not preserved, must be many times greater than the number alive today. Homing in other gastropods and in the chitons that flee from light appears to be performed by chemoreception along their mucus trails. Updated on March 21, 2018. Others feed on macroscopic 'plants' such as kelp, rasping the plant surface with its radula.

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