may be largely internal; their components are very diverse in form. Slugs and snails The reproductive system of gastropods (slugs and snails) varies greatly from one group to another. Planaria Planaria are flat worms widely used in biological research. There are sexual and asexual planaria. Sexual planaria are hermaphrodites, possessing both testicles and ovaries. Each planarian transports its excretion to the other planarian, giving and receiving sperm. Plants In most plant species, an individual has both male and female sex organs. The life cycle of land plants involves alternation of generations between a sporophyte and a haploid gametophyte. The gametophyte produces sperm or egg cells by mitosis. The sporophyte produces spores by meiosis which in turn develop into gametophytes. Any sex organs that are produced by the plant will develop on the gametophyte. The seed plants, which include conifers and flowering plants, have small gametophytes that develop inside the pollen grains (male) and the ovule (female). Flowers In flowering plants, the flowers contain the sex organs. Sexual reproduction in flowering plants involves the union of the male and female germ cells, sperm and egg cells respectively. Pollen is produced in stamens and is carried to the pistil, which has the ovary at its base where fertilization can take place. Within each pollen grain is a male gametophyte which consists of only three cells. In most flowering plants, the female gametophyte within the ovule consists of only seven cells. Thus there are no sex organs as such. Fungi The sex organs in fungi are called gametangia. In some fungi, the sex organs are indistinguishable from each other but, in other cases, male and female sex organs are clearly different. Similar gametangia that are similar are called isogametangia. While male and female gametangia are called heterogametangia, which occurs in the majority of fungi. See also Andrology Emasculation Genital modification and mutilation Hermaphrodite Human sexuality Hysterectomy Intimate part Obstetrics and gynaecology Oophorectomy Orchiectomy References Further reading