1. The gametic fusion takes place at the time of fertilisation when sperm and ovum fuse to form a diploid zygote.
2. The zygote is divided by mitotic division during its embroynic life and post embryonic life to form a well developed individual.
3. A mature individual produces gametes by gametogensis. Reductional division takes place at this stage and results in the formation of haploid gametes.
Example. If a parent cell has 16 chromosomes then in daughter cells due to meiotic division number of chromosomes is reduced to eight.
Mitosis. It is called equational division because number of chromosomes and amount of DNA in daughter cells remain equal to parent cells.
Example. If a parent cell has 18 chromosomes, then in daughter cells formed by mitosis have each 18 chromosomes.