Gdz Biologiia 7 Sumatokhin Klass Dvukhstvorchatye Molliuski Onlain May 2026

: They possess an open circulatory system with a heart and vessels.

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 : They possess an open circulatory system with

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

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

: They breathe through plate-like gills (ctenidia) located in the mantle cavity.

: Many species, such as scallops and oysters, are significant food sources for humans. Freshwater pearl mussels are also cultivated for pearl production.

: By filtering vast amounts of water, bivalves like mussels and oysters act as natural water purifiers in ecosystems.