What are invertebrates?

Invertebrates are animals without backbones; the broad term covers many evolutionary lineages rather than a single close-knit group.

Major groups

Insects and spiders are arthropods; snails and octopuses are molluscs, sea stars are echinoderms and corals are cnidarians. Sponges are animals too. Rigid shells, exoskeletons, hydrostatic support and soft bodies are very different body plans. Some live in water, others in soil or on land. A wormlike appearance can occur in distant lineages, so shape alone does not establish kinship. Many invertebrates are small and easy to overlook.

Why they matter

Many invertebrates pollinate flowers, decompose organic material, work the soil or act as prey and predators in food webs. Seafloor communities may create habitat. Eggs, larvae and adults can require different conditions. Conservation should consider the habitat and functions of these smaller organisms, not only conspicuous large animals.