Gdz Biologiia 7 Sumatokhin Klass Dvukhstvorchatye Molliuski Onlain ⚡

: 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. : Unlike gastropods (snails), bivalves lack a distinct head

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

: 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). Unio (painter's mussel)

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.