Gdz Biologiia 7 Sumatokhin Klass Dvukhstvorchatye Molliuski Onlain May 2026

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

: 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

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 Pasechnik, these organisms are studied for their unique

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

: 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).

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