Teeth Specialized to Diet

close up photograph of tree kangaroo in tree eating during the day

Biological Strategy

Kangaroos and relatives

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Image: Eric Kilby / Flickr / Some rights reserved

Manage Mechanical Wear

A living system is subject to mechanical wear when two parts rub against each other or when the living system comes in contact with abrasive components in its environment, such as sand or coral. Some abrasive components are a constant force, such as finger joints moving, while others occur infrequently, such as a sand storm moving across a desert. Living systems protect from mechanical wear using strategies appropriate to the level and frequency of the source, such as having abrasion-resistant surfaces, replaceable parts, or lubricants. For example, human joints like shoulders and knees move against each other all day, every day. To protect from mechanical wear, a lubricant reduces friction between the cartilage and the joint.

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Physically Break Down Living Materials

Living materials are those that are part of living systems (whether currently or formerly alive). For example, a fallen log, although dead, is considered a living material. Breaking down or breaking up living materials is important for living systems that feed on them, as well as in facilitating the decomposition of organic matter. Breakdown increases the material’s surface area exposed to moisture, fungi, bacteria, and other living systems, many of which use enzymes and other chemicals to further break it down. But living materials can be difficult to break down because, for their own survival, their composition must provide support and protection. Therefore, living systems require mechanical means (such as grinding, tearing, or chewing) to manipulate these materials, as well as strong materials that can overcome resistance. For example, small beetles that chew through wood have large, strong jaws that enable them to cut through this tough material.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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The teeth of different macropod species are adjusted to their diet through specializations that address their specific mechanical digestion needs, including crushing and shearing.

“All wombat teeth are open-rooted. Macropod dentition varies with diet. Potoroos and bettongs consume invertebrates, fruit, and seeds. They have large premolars and a straight molar row with all teeth in occlusion. Molars are adapted for crushing. Browsing macropods- such as pademelons, tree kangaroos, quokkas (Setonix brachyurus), and swamp wallabies (Wallabia bicolor) – still have a straight molar row, but the premolars are smaller and the molars can both shear and crush. The grazing macropods have a vestigial premolar and curved molar row with only the first two molars being in occlusion at any one time. The molars are adapted for shearing. This group, along with elephants and manatees, exhibits the phenomenon of molar progression. As the anterior two molars are worn, they are shed with the posterior molars moving forward, for a total of four molars. The exception is the nabarlek (Peradorcas concinna), which has an unlimited supply of molars.” (Fowler and Miller 2003:289)

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