Gdz Biologiia 7 Sumatokhin Klass Dvukhstvorchatye Molliuski -

: Some species (pearl oysters) produce pearls and mother-of-pearl (nacre) used in jewelry.

: Consists of two symmetrical valves connected by a flexible ligament and a "lock" (hinge). gdz biologiia 7 sumatokhin klass dvukhstvorchatye molliuski

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 : Some species (pearl oysters) produce pearls and

: 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)

: Species like oysters, mussels, and scallops are important food sources for humans and marine life.

(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

: 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.