: The body is laterally compressed and divided into two main parts: the trunk and the wedge-shaped foot . Unlike gastropods, bivalves lack a head, tentacles, and eyes.
Mouth (near the foot), stomach, liver, and intestine. They lack a radula (grating tongue). Plate-like gills (ctenidia) located in the mantle cavity. Excretory Two kidneys that open into the mantle cavity. Nervous Simplified, consisting of three pairs of ganglia. Ecological and Economic Importance gdz biologiia 7 sumatokhin klass dvukhstvorchatye molliuski
: They are filter feeders . Water enters through an inhalant siphon, passes over the gills where food particles are trapped, and exits through an exhalant siphon. : The body is laterally compressed and divided
: Like most mollusks, they have an open circulatory system where the heart pumps blood into the body cavity. Internal Anatomy Summary Characteristic Digestive They lack a radula (grating tongue)
(class Bivalvia ) are a unique group of aquatic mollusks characterized by a shell consisting of two hinged valves and, most notably, the absence of a head . In the Grade 7 Biology curriculum by Sumatohin, they are studied as essential bio-filters and members of aquatic ecosystems. Key Biological Features
: Swan mussels ( Anodonta ), thick-shelled river mussels ( Unio ), and giant clams ( Tridacna ).
: Some species (pearl oysters) produce pearls and mother-of-pearl (nacre) used in jewelry.


