Video narration
Does every animal embryo need sperm to begin? Usually, an egg joins sperm, and the cell divides into an embryo. But an egg is not empty. In some animals, the egg can switch on by itself and start dividing. This is parthenogenesis: reproduction from an unfertilized egg. To develop, the egg needs the right chromosome set: genetic instructions its cells carry. Without sperm's second set, it maintains or restores the needed set, depending on the species. Then one cell divides into two, then many, building an embryo. The offspring is not always an exact clone. Its genes can be very similar to the parent, but the result depends on how its chromosome set is restored. This happens only in some animals. So yes: an unfertilized egg can begin an embryo without sperm. That is parthenogenesis, though the offspring may not be an exact clone.