The production of new organisms from two parents by making use of their sex cells is called sexual reproduction.
In sexual reproduction more viable variations are observed than asexual reproduction as two parent are involved. In case of asexual reproduction single parent organism gives rise to offsprings which are genetically identical to their parents. This limits the scope of variation in characters of off springs. Due to sexual reproduction the extent of variation is much large and therefore choices of evolution is also high. The variations in the characters of the obtained offsprings from sexual reproduction enable them to adopt according to the environment and struggle for their existence. Over a period of time the characters accumlate within the species and the formed species gives rise to new species and this process goes on.