Decomposers (saprotrophs) are organisms such as bacteria and fungi that break down the organic matter in the dead bodies of plants and animals into simple nutrients.

An exoskeleton (external skeleton) is common in arthropods like insects, spiders, and crustaceans.

An element in a solid state has atoms or molecules that are constricted and do not move freely. Solids maintain a constant volume and shape and exist at a lower temperature than liquids or gases.

The narrowest classification of life, species, contains organisms that are so similar that they can only reproduce with others of the same species.