Gastropods Gastropods are single-shelled or shellless animals. They are found both in marine environments and in fresh water and even in the terrestrial environment. Whelks, sea slugs and snails are examples of animals in this group. Super curiosity! Shells of the species Monetaria moneta began to be used as currency around the 11th century BC and, until the 19th century AD, continued to be used in transactions in some regions of Africa. Bivalves These beings have a shell divided into two parts forming a small box! Inside are your organs. They can live buried in the sand, stuck to rocks or even resting at the bottom of the sea! Super curiosity! Pearls are produced by some bivalves! Whenever foreign elements, such as grains of sand or pieces of coral, enter the organism of these animals, the deposition of nacre (a shiny-looking substance) begins involving this possible invader. Thus forming the pearls! Cephalopods Its main feature is the presence of feet that come out of the base of its head. They may have internal shells (such as squid), external shells (such as nautilus) or the absence of shells (such as octopuses). Super trivia! Nautilus shells are formed by different chambers that can fill and empty with gas, to control the buoyancy of these animals. Making them real floating machines! WHY SHOULD WE NOT TAKE THE SHELLS OFF THE BEACH? Calcium carbonate is found in the shells, which helps in the formation of the skeleton of some marine animals. In addition, they serve as protection and shelter for other beings, in the construction of bird nests, substrate for marine flora and to make the marine environment stable.