Examples of index fossils. Index fossils (also known as guide fossils, indicator fossils or zone fossils) are fossils used to define and identify geologic periods (or faunal stages).
Methyl cellulose. Methyl cellulose (or methylcellulose) is a chemical compound derived from cellulose. It is a hydrophilic white powder in pure form and dissolves in cold (but not in hot) water, forming a clear viscous solution or gel.
This organic compound, which is considered the most abundant on earth, is even excreted by some bacteria. Cellulose provides structure and strength to the cell walls of plants and provides fiber in our diets. Although some animals, such as ruminants, can digest cellulose, humans cannot. Cellulose falls into the category of indigestible carbohydrates known as dietary fiber. In recent years, cellulose has become a popular food additive due to its unique chemical and physical properties when combined with water.