Gdz Biologiia 7 Sumatokhin Klass Dvukhstvorchatye Molliuski Onlain Link

: 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. : The nervous system is simplified, consisting of

: They breathe through plate-like gills (ctenidia) located in the mantle cavity. : Unlike gastropods (snails), bivalves lack a distinct head

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

: 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).

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

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