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This figure shows some of the much more common and familiar mollusks.

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Structure and role of Mollusks

Mollusks room a very diverse phylum. Some mollusks are nearly microscopic. The largest mollusk, a colossal squid, may be as lengthy as a college bus and also weigh over fifty percent a ton! The an easy body arrangement of a mollusk is shown in Figure below. The main distinguishing feature is a tough outer shell. It covers the peak of the body and encloses the inner organs. Most mollusks have actually a distinctive head region. The head may have actually tentacles for sensing the environment and also grasping food. There is typically a muscular foot, which might be provided for walking. However, the foot has actually evolved modifications in many types to be provided for other purposes.


Basic Mollusk body Plan. The straightforward body setup shown right here varies amongst mollusk classes. Because that example, numerous mollusk species no longer have actually shells. Perform you know which ones?

Two distinctive features of mollusks are the mantle and radula (see Figure above). The mantle is a layer of tissue that lies between the shell and also the body. The secretes calcium carbonate to type the shell. It forms a cavity, dubbed the mantle cavity, between the mantle and also the body. The mantle cavity pumps water for filter feeding. The radula is a feeding body organ with teeth made of chitin. The is located in prior of the mouth in the head region. Herbivorous mollusks use the radula to scrape food together as birds off rocks. Predatory mollusks usage the radula to drill holes in the shells of their prey.

Mollusks have actually a coelom and also a finish digestive system. Their excretory system consists of tube-shaped organs dubbed nephridia (see Figure above). The organs filter garbage from body fluids and release the waste right into the coelom. Terrestrial mollusks exchange gases through the bordering air. This occurs across the lining that the mantle cavity. Aquatic mollusks “breathe” under water v gills. Gills are thin filaments that absorb gases and also exchange them in between the blood and also surrounding water.

Mollusks have a circulatory device with one or 2 hearts the pump blood. The heart is a muscular organ that pumps blood through the circulatory mechanism when its muscle contract. The circulatory system might be open or closed, relying on the species.

See more: Which Level In A Food Web Contains The Highest Amount Of Total Available Energy?

The significant classes the mollusks differ in structure and function. You deserve to read around some of their differences in Figure below.