[Invertebrates are particularly useful for analyzing the neural and molecular events underlying learning and memory. The nervous systems of many invertebrates contain only several thousand cells (compared with the billions of cells in the vertebrate...

Invertebrates are animals without backbones. This simple definition hides the tremendous diversity found within this group which includes protozoa (single-celled animals), corals, sponges, sea urchins, starfish, sand dollars, worms, snails, clams,...

Any animal that lacks a vertebral column, or backbone. They include the protozoans, annelids, cnidarians, echinoderms, flatworms, nematodes, mollusks, and arthropods. More than 90% of living animals are invertebrates. Worldwide in distribution,...

An animal that does not possess a backbone or spinal column. Such creatures as insects and crustaceans are invertebrates. See also: EXOSKELETON;...

Any of the animals without a vertebral column (i.e. a backbone composed of individual vertebrae); not one of the...

Any species of animal lacking a back...

An invertebrate is an animal lacking a spinal column. The group includes 97% of all animal species — all animals except those in the Chordate subphylum Vertebrata (fish, reptiles, amphibians, birds and mammals). Carolus Linnaeus' Systema Naturae...