Recognize that all organisms are composed of cells and that many organisms are unicellular and must carry out all life functions in one cell. 3.1.6.A5 Describe basic structures that plants and animals have that contribute to their ability to make or find food and reproduce.
Crabs are crustaceans and all crustaceans belong to the taxonomic domain of Eukarya, which are characterised by having cells with nuclei. Eukarya covers all organisms in the Kingdom Animalia, as well as the Kingdoms Plantae, Fungi and Protista.
Crabs are crustaceans of the infraorder Brachyura, and they make up about half of all decapods, or 10-footed creatures. There are 6,793 species of crab. They are a diverse group, ranging in size from the tiny pea crab, which is less than 1 inch across, to the Japanese spider crab, which has a leg span of up to 13 feet.