Many invertebrate animals (such as shelled mollusks) have exoskeletons in the sense of external hard parts. But if one speaks of an exoskeleton one mostly means that of arthropods (i.e. insects, spiders, myriapods and crustaceans).
Exoskeletons contain rigid and resistant components that fulfil a set of functional roles including protection, excretion, sensing, support, feeding and (for terrestrial organisms) acting as a barrier against desiccation. Exoskeletons first appeared in the fossil record about 550 million years ago, and their evolution has been seen as critical as a driving role in the Cambrian explosion of animals that took place after this time.
The exoskeleton ( exoskeleton suit) is a device intended to restore the lost motion functions of a person or other living being. The exoskeleton also serves to increase human muscle strength and range of motion by means of an external skeleton and drive elements.
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- Geometry and Pattern in Nature 3: The holes in radiolarian and diatom tests Archived 2005-12-16 at the Wayback Machine