For further study and visual aids, students can refer to educational platforms like Yaklass or watch lesson summaries on YouTube .
: They possess an open circulatory system with a heart and vessels.
: They breathe through plate-like gills (ctenidia) located in the mantle cavity. For further study and visual aids, students can
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
: By filtering vast amounts of water, bivalves like mussels and oysters act as natural water purifiers in ecosystems. Pasechnik, these organisms are studied for their unique
: The nervous system is simplified, consisting of three pairs of ganglia. Ecological and Economic Importance
: Students typically study the Anodonta (swan mussel), Unio (painter's mussel), and marine species like the edible mussel and giant clam. Unio (painter's mussel)
: Unlike gastropods (snails), bivalves lack a distinct head. Their body consists of a torso and a muscular "foot" used for burrowing or anchoring.