The mechanism by which variations are created and inherited is known as heredity.
Heredity is the phenomenon of passing traits from parent to offspring. Sperms and eggs are the gametes produced by reproductive organs of male and females. These are haploid with one set of chromosomes.
*Sperms are the male gametes possessing a head, body and a tail. They either comprise X chromosome or Y chromosome.
*The eggs are the female gametes produced by the ovary. They all comprise of X chromosome.
*During fertilisation, sperm nucleus fuses with egg nucleus to form a diploid zygote.
*Zygote is the future individual. A zygote transforms into embryo which inturn develops into foetus.