Definition: Hard framework, internal or external, which supports and protects softer parts of plant, animal or unicellular organism, and to which muscles usually attach in animals, includes skeletons (derived from Lawrence, 2005).
Definition: Gravel is an environmental material which is composed of pieces of rock that are at least two millimeters (2mm) in its largest dimension and no more than 75 millimeters.
Definition: Component found in mineralized skeletal tissue, (a specialized form of biogenic tissue in which the extracellular matrix is mineralized, and which functions in mechanical and structural support.)
Definition: A structural quality inhering in a bearer by virtue of the bearer's being thicker or more closely packed together; pressed tightly together.
