invertebrate

Invertebrates are animal species that neither possess nor develop a vertebral column, derived from the notochord. By definition, this includes all animals apart from the subphylum Vertebrata. Familiar examples of invertebrates include insects, crabs, lobsters and their kin, snails, clams, octopuses and their kin, starfish, sea-urchins and their kin, and worms. The overwhelming majority of animal species are invertebrates. One estimate in the journal Science put the figure at 97%. Many individual invertebrate taxa have a greater number and variety of species than the entire subphylum of Vertebrata and some of the so-called invertebrates, such as the Chaetognatha, Hemichordata, Tunicata and Cephalochordata are more closely related to the vertebrates than to other invertebrate phyla. This makes the term “invertebrate” almost meaningless for taxonomic purposes.