Genital organs

Sexual reproduction is almost universal in vertebrates; only a very few lizards normally reproduce partheogenetically-without needing (or having) mates. The basic reproductive structures are the gonads-ovary or testis. In this organare produced the gametes-eggs(ova) or sperm-by the union of which in the process of fertilization, the new generation is begun. In all gnathostomes, the are associated with the gonads tubes or ducts (with accesory structures) for the transport of gametes and in certain cases for the protection and nourishment of the growing young within the female body. In addition copulatory organs, which aid in internal fertilization of the eggs, may develop in the region of the external opening of the genital tract. And finally , secondary sexual charactersare frequently found in other bodily structures; sex may affect general body size or proportions, and the development of such fetauresas the plumage in birds , mammary glands in mammals, antlers and horns in ruminants, and beards in our own species.