The basic requirements for sexual reproduction to take place is the involvement of two parents and fusion of their haploid gametes. In the sexual reproduction, a new individual is formed which is diploid in nature, the gametes, one from the male parent and the other from the female parent. Since the new individual formed is diploid in nature, the gametes must be formed by meiosis, so that chromosome number can be reduced to half. When fusion of gametes occurs, the nuclei of these two gametes fuse and the chromosome number is then restored to normal. The zygote, thus, formed is diploid in nature.
Importance of sexual reproduction :
(i) Sexual reproduction involves fusion of male and female gametes from both the parents, thus results in genetic variations in the offsprings.
(ii) Sexual reproduction promotes diversity of characters in offsprings by providing genetic variations.
(iii) These genetic variations, thus lead to evolution of species as well as allow the organisms to become better adapted in the changing environment.