Bivalves have a two-part shell, while gastropods have a single-part shell. Gastropods can also move around more easily than bivalves. Bivalves tend to be stationary, attaching themselves to surfaces with their strong muscles. Both groups of animals also have a head with eyes and tentacles, but bivalves lack a true head region and have gills for filter feeding.
What are bivalves?
Bivalves are a type of mollusc that have two shells, which are hinged together. in previous centuries they were referred to as the Lamellibranchiata and Pelecypoda. They are found in both fresh and saltwater environments and can range in size from a few millimetres to over a meter in length. Some common examples of bivalves include clams, oysters and mussels. Bivalves are also mostly sedentary, meaning they don’t move around very much. Bivalves are filter feeders and use their gills to filter food from the water around them.
Bivalves provide many benefits to humans as food, building materials, and jewellery and also provide other benefits such as stabilizing shorelines and mitigating nutrient pollution.
What are gastropods?
Gastropods are a type of mollusc that has a single shell (or no shell at all). They can also be found in both fresh and saltwater environments, but tend to be larger than bivalves. Some common examples of gastropods include snails and slugs. Gastropods can move quite a bit. Most gastropods move by gliding along on their large, muscular foot. Gastropods are considered scavengers.
The earliest undisputed gastropods date from the Late Cambrian Period, around 500 million years ago.
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