Whether an organism is a carnivore, herbivore, or omnivore, it is a heterotroph and consumes pre-existing foods. An herbivore will be adapted for primarily eating plants and its teeth will be of the type that aid in biting off, gnawing and grinding leaves. Therefore, incisors are important and molars which are flat for grinding plant materials. The digestive system is longer in herbivores, as it takes longer for plants to be digested. Some rumens have the abilitiy to regurgitate and reswallow the plants it eats, like a cow that chews its cud, to help the fibers become digested. Digestion of plant foods begins in the mouth, and ends in the small intestine. Carnivores have a shorter intestine as meats are easier to break down than plants. Their teeth are usually sharper with pronounced canines for tearing meat and shredding meat and sharp molars for aiding in cutting up meat to be swallowed. Protein digestion begins in the intestine and ends in the small intestine. An omnivore consumes plants and animal flesh so they have well developed incisors, canines, premolars and molars, adapted for a wide range of foods. An example of an omnivore is a human or a bear.