22. Fertilization is when

Fertilization is the process by which a sperm cell and an egg cell fuse together to form a single cell called a zygote. This typically occurs in the fallopian tube of a female reproductive system. Once fertilization occurs, the zygote begins to divide and grow, eventually developing into an embryo and then a fetus. Fertilization is a crucial step in reproduction and is necessary for the continuation of a species.