All metazoans, if or if not capable of propagating asexually, produce special cells termed as gametes. The gametes may be either male gametes or sperms or female gametes (ova). Syngamy follows throughout which a sperm fertilizes an ovum producing a zygote. The zygote develops and finally produces an adult. During syngamy, there is doubling of chromosomes; the zygote and its derivative cells are diploid. To prevent repeated doubling of chromosomes, there is meiosis or reduction division during the production of gametes. In this procedure chromosome number is reduced to half (haploid number). The cycle is repeated, and the chromosome number is maintained.