Sexual reproduction is the production of new organisms from the combination of genetic material from the gametes of two opposite sexes. Asexual reproduction is the process in which a single organism produces a new, identical organism. In most vertebrates, the male sex cell is the sperm, and the female sex cell is the egg. These cells are also called gametes. After fertilization, the new cell begins to divide (mitosis) and develop into a new individual (zygote).