Klass Dvukhstvorchatye Molliuski Onlain — Gdz Biologiia 7 Sumatokhin

: The body is laterally compressed and enclosed in a bilateral shell. This shell consists of three layers: an outer organic layer (periostracum), a middle calcareous layer, and an inner pearly layer (nacre).

: By filtering vast amounts of water, bivalves like mussels and oysters act as natural water purifiers in ecosystems. : The body is laterally compressed and enclosed

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

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 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

For further study and visual aids, students can refer to educational platforms like Yaklass or watch lesson summaries on YouTube .

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