Arthropods are invertebrates in the phylum Arthropoda. They possess an exoskeleton with a cuticle made of chitin, often mineralised with calcium carbonate, a body with differentiated (metameric) segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They are an extremely diverse group, with up to 10 million species.
Protaetia cuprea (copper chafer). Beetles are the most diverse order of arthropods.
Cicada climbing out of its exuviae while attached to tree
Long bristles (setae) of a Tliltocatl albopilosus tarantula
Head of a wasp with three ocelli (center), and compound eyes at the left and right
Invertebrates is an umbrella term describing animals that neither develop nor retain a vertebral column, which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum Vertebrata, i.e. vertebrates. Well-known phyla of invertebrates include arthropods, mollusks, annelids, echinoderms, flatworms, cnidarians and sponges.
Invertebrate
The fossil coral Cladocora from the Pliocene of Cyprus
Image: European wasp white bg 02
Image: Platycryptus Undatus Female
