In human beings the males produce the male gamete called sperms. Sperms which is a single cell is very small in size. it has three parts - a head, a middle piece and a tail.
The female gamete called ova or egg is produced by ovaries. Every ova is a single cell. One matured ova is released by one of the ovaries every month.

When a male and a female gamete come in contact with each other they fuse. The male sperm enters the female ova and the nucleus of the sperm fuses with nucleus of the ova and results into a single nucleus. This whole process is called fertilization. In short fertilisation is the fusion of male and female gametes.

In human beings male reproductory organ consists of  are a pair of testes, sperm ducts and a penis. Testes are responsible for producing male gametes called sperms. 

In sexuaal reproduction the gamete from the father and the gamete from the mother, fuse to produce the zygote. This zygote develops into baby. Since it involves the fusion of gamete of bothe the parents,  thus, the baby depends both hi father and mother. 

In human beings the female reproductory organ consists of a pair of ovaries, oviducts or fallopian tubes and the uterus. Ovaries produce female gamete called ova, which fertilize with male sperm in female fallopian tube and travels to uterus for further development.