Sexual reproduction involves two organisms, the male and the female in the process of producing the offspring. Sexual reproduction provides greater variations in the DNA thereby making the offspring adapted for better survival. Sexual reproduction ensures a mixing of the gene pool of the species. Due to genetic recombination, variations occur in the process of sexual reproduction.

During Sexual reproduction the combination of DNA from two parents would result in the offspring having twice the amount of DNA. To solve this problem, sexually reproducing individuals have special germ cells (gametes) with only half the normal number of chromosomes and, therefore half the amount of DNA compared to the other cells of the body. When such germ cells from two individuals untie during sexual reproduction the normal chromosome number and DNA content are restored.

In multicellular organisms body designs become more complex, the germ cells also specialize. One germ cell is large and contains the food stores while the other is smaller and likely to be motile. The motile germ cell is called the male gamete and germ cell containing the stored food is called the female gamete.