Fossils may be defined as the remains of the organisms which have been preserved in the form of molds or cast in rocks etc. since prehistoric ages.
When a plant or an animals die, their remains fall on the ground. Over a period of time, their body gets covered by sediments brought by rivers, winds etc. These sediments keep on getting accumulated for over hundreds of years and when that land gets eroded, the fossils can be seen clearly. Thus, the process of accumulation of dead remains of plants and animals for over hundreds of years results in the formation of fossils. There are two components to this estimation of age of fossils.
They are direct traces of evolution from the geological past. they also help in determining the past climatic conditions and the variations that have occurred in animals over the time.
