The greatest diversity that exists today is a result of 3500 million years of evolution from simple organisms of the past. Evolution can be defined as the development of complex organisms from pre-existing simpler organisms over a period of time. Evolution may also be defined as a slow, continuous and an irreversible process of change. It involves series of changes that occur in a population over a number of generations.
According to theory of organic evolution the life on earth has undergone a series of changes over a million of years. Paleontological evidences, bio geographical evidences, evidences from comparative morphology and anatomy and embryological evidences support theory of organic evolution.
Natural selection formed the central framework of Darwin's hypothesis on evolution. Natural selection brings about perpetuation of certain characteristics and elimination of others.
Artificial selection, adaptive radiations etc led to evolution.
Variations are essential for evolution. Mendel conducted series of experiments and talked about inheritable factors influencing phenotypes. Later, Hugo de vries brought forth the idea of mutations as large differences appearing suddenly in a population. He believed that mutations caused evolution and not the minor variations as explained by Darwin.
Our characters are present in genes in chromosomes. These genes are transferred from our ancestors. This is called heredity. We get our characters through this process. Dominant one shows character and recessive one remains hidden . But while transferring both get transferred