👉 Polyspermia, also known as sexual reproduction or fertilization, is the process by which a sperm (a type of cell that contains genetic material) penetrates an egg and fertilizes it. This happens in mammals, birds, fish, and other animals, but not in plants. In humans, during sexual reproduction, sperm enters the female reproductive tract through an opening called the fallopian tube. The sperm then swim down into the uterus and, after reaching the ovum (egg),