: Species like oysters, mussels, and scallops are important food sources for humans and marine life.
: As filter feeders, they clean bodies of water by removing organic suspension. gdz biologiia 7 sumatokhin klass dvukhstvorchatye molliuski
(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 : Species like oysters, mussels, and scallops are
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 In the Grade 7 Biology curriculum by Sumatohin,
: 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.