Third, magnetism in rocks can be used to estimate the age of a fossil site. This method uses the orientation of the Earth's magnetic field, which has changed through time, to determine ages for fossils and rocks.
Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In humans, cellulose acts as a hydrophilic bulking agent for feces and is often referred to as a  dietary fiber .
Cellulose and plant cells. Since cellulose is the main building material out of which plants are made, and plants are the primary or first link in what is known as the food chain (which describes the feeding relationships of all living things), cellulose is a very important substance.s the chief constituent (or main ingredient) of the cell walls of plants, cellulose performs a structural or skeletal function. Just as our hard, bony skeletons provide attachment points for our muscles and support our bodies, so the rigidity or stiffness found in any plant is due to the strength of its cell walls.