Final answer:
Fertilization is the union of a sperm and egg, resulting in a zygote, which then undergoes mitotic cell divisions and develops into an embryo. This process includes the merging of genetic material from both gametes creating a new organism. The zygote's division and specialization of cells lead to embryonic development.
Step-by-step explanation:
The beginning stages of reproduction involve two primary cells: the sperm from the male and the egg from the female. These reproductive cells are known as gametes. Fertilization occurs when a sperm successfully penetrates the egg, triggering the completion of meiosis in the egg and thereby forming a single-celled entity known as a zygote.
The process begins with the fusion of the sperm’s and egg’s plasma membranes, which brings together their genetic material, each containing one set of chromosomes. Once inside the egg, the sperm’s tail falls off, and its nucleus merges with the egg’s nucleus. This merged nucleus contains the full genetic blueprint for a new individual, housing a diploid set of chromosomes—half from the sperm and half from the egg.
This zygote then starts a process of rapid cell division, known as mitosis, where it divides into two cells, then four, eight, and continues multiplying. These subsequent cell divisions eventually lead to the development of various organs and body parts of a growing human. Following the stages of fertilization, cleavage, blastulation, and implantation, the cells become a more complex structure, known as an embryo, which eventually implants into the lining of the uterus to continue its development.