The following organisms are all invertebrates: worms, medusas, molluscs, and arthropods (crustaceans, spiders, and insects)
A clam is a mollusc, a crab is a crustacean, and a dragonfly is an insect. Crustaceans and insects belong to the group of arthropods.
Water-dwelling invertebrates get their oxygen by either:
using specialized organs called gills to filter oxygen from water.
occasionally coming up to the surface to breathe oxygen from the atmosphere.
Many species of insects undergo a process of metamorphosis. A complete metamorphosis consists of the egg, larval, pupal, and adult stages. An incomplete metamorphosis lacks a pupal stage.
