As far as feeding styles go, the animal kingdom divides into three basic categories: carnivores, omnivores and herbivores. Carnivores gain their nutrition by eating flesh. Omnivores sustain themselves on a combination of both meats and plants. Herbivores, meanwhile, receive energy via exclusive consumption of plants.
Plants Only, Please
Herbivores' bodies are are designed to only feed on plants, and in some cases only on specific kinds and parts of plants. The majority of herbivores have degrees of diversity to their feeding plans, but a few of them have extremely limited menus. Koalas (Phascolarctos cinereus), for instance, generally eat only eucalyptus trees. Pandas (Ailuropoda melanoleuca), similar herbivores, rarely eat anything other than bamboo.
Many ungulates are herbivores. Ungulates are hooved animals such as deer, gazelles, giraffes, horses and other livestock. Outside of ungulates, many other diverse animals are herbivores, including rabbits, hippopotamuses, beavers, elephants and grasshoppers.
Herbivores have high energy demands. If they don't receive sufficient energy, they simply can't survive. This is why so many herbivores occupy their entire days busily feeding -- consider grazing cows. They need to devote a significant amount of time scouring for the vital nutriment their bodies require.
Pointy front teeth are a carnivore trademark, and those of herbivores aren't as razor-edged. Herbivores don't need to calm prey animals down, after all. Meat-eating animals lack flat molars, which herbivores employ for crushing their food down. When herbivores feed, they rely on their molars and premolars the most. Herbivores' front teeth are responsible for retrieving plants. The teeth tug at plants to grab them and then adeptly rip them apart. Not all herbivores' upper jaws are equipped with front teeth. These have tough pads in place of the teeth. They grab food by using the combined strength of their bottom teeth and upper pads. This action enables them to adequately rip into their food finds.
Carnivorous animals possess acidic saliva, which means that they're capable of starting to digest things essentially as soon as they put them in their mouths. Herbivorous animals, in contrast, have alkaline saliva, which means the digestion process doesn't begin as promptly. The plants they eat undergo a preparatory process before digestion commences. People also have alkaline saliva.
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