Phylum Arthropoda has the largest number of species. Arthropods have a segmented body that is covered by an exoskeleton. The exoskeleton is used for protection and is where muscles are attached. Arthropods go through a process called molting. Molting is when the arthropod sheds its exoskeleton and replaces it allowing it to grow. Animals in the phylum all have jointed appendages, which include antennae and jointed legs. Movement of these appendages is controlled by a complicated system of muscles which is divided into smooth and striated muscle. This phylum includes insects, crustaceans, scorpions and centipedes.