Bone-like structures found in the mouths of many vertebrates, used for biting and chewing. Some also use teeth for hunting and defensive purposes. The roots of teeth anchor the teeth in the jaw; they are covered by gums. Teeth are not technically made of bone, but rather of multiple tissues of varying density and hardness. The cellular tissues that develop as teeth originate in the the ectoderm. The general structure of teeth is similar across the vertebrates, but there is variation in placement and form. Monophyodonts develop only one set of teeth for use in adulthood, while polyphyodonts develop many sets of teeth.