Female gamete (sex cell) before fertilization. In mammals it is called an egg, and is produced by a special cell division called
meiosis in the ovaries during the
menstrual cycle. In plants, where it is also known as an egg cell or oosphere, the ovum is produced in an ovule. The ovum does not move by itself. It must be fertilized by a male gamete before it can develop further, except in cases of
parthenogenesis.
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