Gdz Biologiia 7 Sumatokhin Klass Dvukhstvorchatye Molliuski Onlain Today

The Class Bivalvia (Двустворчатые моллюски) is a group of aquatic mollusks characterized by a shell composed of two hinged parts. In the 7th-grade biology curriculum by S.V. Sumatokhin and V.V. Pasechnik, these organisms are studied for their unique evolutionary adaptations to a sedentary lifestyle. Key Biological Features

: Students typically study the Anodonta (swan mussel), Unio (painter's mussel), and marine species like the edible mussel and giant clam.

: Many species, such as scallops and oysters, are significant food sources for humans. Freshwater pearl mussels are also cultivated for pearl production. Pasechnik, these organisms are studied for their unique

: Unlike gastropods (snails), bivalves lack a distinct head. Their body consists of a torso and a muscular "foot" used for burrowing or anchoring.

: They possess an open circulatory system with a heart and vessels. Freshwater pearl mussels are also cultivated for pearl

: The nervous system is simplified, consisting of three pairs of ganglia. Ecological and Economic Importance

: By filtering vast amounts of water, bivalves like mussels and oysters act as natural water purifiers in ecosystems. Unio (painter's mussel)

: Most bivalves are filter feeders. They draw water into their mantle cavity through a siphon, where specialized gills trap organic particles. Internal Systems