Anatomical Differences – Omnivores
Omnivores are the most flexible eaters of the animal kingdom. They eat both plants and meat, and many times what they eat depends on what is available to them. When meat is scarce, many animals will fill their diets with vegetation and vice versa. It is easy to understand why the species “dog” was included in this classification, however, was it not for that fact that the “dog” have no flat molars.
Anatomical features common to omnivores confirm their adaptation for a mixed meat and plant-based diet.
- Medium Length Digestive Tracts that provide the flexibility to digest both vegetation and animal proteins.
- Flat Molars and Sharp Teeth developed for some grinding and some tearing.
- Saliva contains Carbohydrate-Digesting Enzymes, amalyze which is responsible for the majority of starch digestion.
For comparison, we want to introduce the American Black Bear [Wikipedia] to you. A true omnivore, the North American bear has a very opportunistic diet. What they eat depends on what is easily available and that changes with the seasons: tree buds, plants (including pollen and flowers), roots, berries, seeds, nuts, bugs of all kinds, and occasionally, even fish or meat. Like our species “dog”, a black bear has 42 teeth that work perfectly for such a varied diet. Unlike our species “dog”, the bear does not have accentuated carnassial teeth. Not all mammals developed carnassial teeth. Mesonychids [Wikipedia], for example, had no carnassial adaptations, and as a result, the blunt, rounded cusps on its molars had a much more difficult time reducing meat. Our black bear do have incisors, canines, pre-molars and molars, but unlike wolves and cougars, a black bear’s molars are more like ours. Just like we use our broad, flat molars for grinding up a raw carrot, bears use theirs for grinding acorns, nuts, and all the vegetation they eat. Unlike the species “dog”, the black bear have two molars on top and three on the bottom of each side.
The drawings below demonstrate the chewing surfaces of the teeth, compared to Raccoon, Red Panda and Giant Panda, along with a visual summary of their surface areas. These surface areas affects how well they can grind through vegetation and nuts.
Like herbivores and carnivores, omnivores are a very important part of the food chain or web. Creatures in the food chain or web are also classified into a system called the trophic system (food chain) [Wikipedia]. The trophic system has three levels. The top level includes omnivores and carnivores. The second level includes herbivores (animals that eat vegetation) and the bottom level includes living things that produce their own energy, like plants.
Omnivores help keep in check both animal populations and vegetation growth. Removing an omnivore species can lead to vegetation overgrowth and an overabundance of any creatures that was part of its diet.
Omnivores have very distinctive teeth that help with the digestion of their varied diets. They often have long, sharp, pointed teeth to rip and cut meat and flat molars to crush plant material. One good example is the huuman mouth. Huumans have canines and incisors that bite and tear into food and molars and premolars that are used to crush food. While most animals have sharper, more pointed teeth for tearing and ripping, the concept is the same.
Some omnivores, such as chickens, have no teeth and swallow their food whole, according to the Animal Nutrition Handbook from the Auburn University College of Agriculture. The food is softened in the stomach by hydrochloric acid and digestive enzymes. Then, the food gets broken down in the gizzard, a strong digestive muscle, and rocks that the chicken has swallowed.
Omnivores have a different digestive system from either carnivores or herbivores. Carnivores have a very simple digestive tract because meat is easy to digest. Herbivores, on the other hand, can have very complex digestive systems that can include multiple stomach chambers and regurgitating food for re-chewing, because plant materials are much harder to digest.
Omnivores, for the most part, are somewhere in the middle. They have a limited ability to digest certain plant materials. Instead of trying to process the harder materials, though, the omnivore’s digestive tract sends the material out as waste.
Why did some animals evolve to eat meat or vegetation while others eat both? It seems to come down to availability of resources. In terms of evolving to be a meat eater or plant eater, basically, any place there is available energy you will have a ‘niche’ for a species to fill in the ecosystem.
Common theory state that meat eaters evolved in areas where meat was plentiful while herbivores evolved in areas where vegetation was plentiful. Omnivores are the most adaptive of all the species and thrive in a larger range of environments.