Evolution. Evolution is the sequence of gradual changes which take place in the primitive organisms over millions of years in which new speices are produced.
How it occurs?
It is through the constant process of evolution taking place in the organisms since the origin of life that such and enormous variety of plants and animals have come to exist on this earth at present.
There is an inbuilt tendency to variation during reproduction due to errors in DNA copying and as a result of sexual reproduction.
Relationship between fossils and evolution :
Fossils are the remains of impressions of dead plants or animals which died millions of year ago. The study of fossils helps us to know about the evolution of species. Fossils tell us how new species are developed from the old. Fossils provide evidence of evolution by revealing characteristics of past organisms and the changes that have occured in these organisms to give rise to present organisms. Therefore, fossils have an importance in deciding evolutionary relationship.
For example, a fossil called Archaeopteryx has feathered wings like birds but teeth and tail like reptiles hence suggesting that birds and reptiles had a common ancestor.
