Which process involves male and female reproductive cells joining to form a new cell?

Fertilisation is the process in which male and female reproductive cells, or gametes, join together to form a new cell called a zygote. This event marks the beginning of a new organism's development. In organisms that reproduce sexually, the male gamete (sperm) and the female gamete (egg) combine their genetic material, resulting in a zygote that has a complete set of chromosomes—half from each parent. This genetic combination is crucial for genetic diversity and the continuation of species.

In contrast, implantation refers to the process where the fertilised egg attaches to the lining of the uterus, which occurs after fertilisation. Mitosis is the process by which a single cell divides to produce two identical daughter cells, primarily for growth and repair, and does not involve gametes. Binary fission is a form of asexual reproduction seen in prokaryotes, where a single organism divides into two independent organisms, and it also does not involve the combination of male and female reproductive cells.