The DNA replication processes, though precise are not absolutely accurate and thus mistakes can be made. These mistakes in DNA copying mechanism result in variations in the population, which are necessary for the survival of individual in a population. This process of creating variations speeds up in sexual reproduction. Here, two individuals of a population, with different patterns of accumulation of variations, interact and participate in producing a new generation. These variations are unique. Thus, the diversity in characters of offsprings is promoted in sexual reproduction.