Assignment 12: (continued)

Mammalian teeth are also adapted to the diet of the species. There are four types of teeth, although not all mammals have all types. In the front of the mouth are incisors, teeth that function in nipping or chiseling. On each side of the incisors may be found the canines, useful in biting and piercing prey. Behind the canines are "cheek teeth": the premolars, that do some grinding, and the molars, that do most of the grinding and chewing. The size and shapes of these tooth types are correlated with the different diets of mammalian species.

Carnivores use their dentition not only for initial food processing, but often for acquisition as well. Canines are often used to pierce and kill prey, while the premolars and molars are designed for slicing and shearing meat into pieces small enough to swallow. The upper and lower cheek teeth of carnivores come together much like a pair of scissors, slicing down past one another in a shearing action.  Muscles in the jaws of carnivores are designed to put a great deal of force behind this motion. 

For herbivores, the challenge lies less in obtaining their food (they don’t need to chase down grass!) than in processing it to extract what few nutrients are available. Generally, herbivores that consume leafy vegetation use their teeth as a grinding surface on which to reduce the particle size of the material. The muscle attachments in the jaws of herbivores are designed for lateral (back and forth) movement of the upper and lower jaws against one another, with the surfaces acting as a grinder. The cellulose present in grasses is highly abrasive to teeth. Herbivores that gnaw woody plants possess teeth that can grow continuously throughout the animal’s lifetime. These are known as rootless teeth--the beaver is a good example. 

Omnivores consume foods that vary in physical composition. While their teeth are not as specialized as those found in carnivores and herbivores, omnivore teeth are quite adequate for moderate amounts of shearing and grinding. Seed coats and insect exoskeletons are similar in that they possess a tough outer coating, so omnivore teeth are optimal for breaking open these outer casings to make available the more digestible foods inside. They are also well designed for opening fruits and eating young, less abrasive vegetation.  

Skulls showing the dentition of several mammals

Study the teeth of these mammals and think about how they are adapted to different diets. Then identify the following skull photographs as a herbivore, carnivore or omnivore based on dentition and submit your answers for questions 13-15.

Skull #1

Skull #2

Skull #3

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