Correlation Between Diet & the Evolutionary Adaptations of Vertebrate Digestive Systems

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  • 0:01 Dietary Adaptations
  • 0:42 Dental Adaptations
  • 1:47 Stomach & Intestines
  • 3:24 Symbiosis
  • 5:21 Lesson Summary
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Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Diet plays a big role in influencing an animal's digestive system's adaptations. This lesson show you how diets influence everything from the shape of teeth to the digestive tract to peculiar dietary habits.

Dietary Adaptations

You are what you eat. You've heard that one before, haven't you? It's a bit of an exaggeration. You won't really become a doughnut even though you may munch on them all day, but your body may modify its shape in response to the empty calories.

Vertebrate digestive systems have evolved over many years to adapt to or correlate with the diet an animal needs to survive. Cows won't turn into grass, but everything from their teeth to their stomach is a reflection of the fact that they eat grass. This lesson goes over some of the general digestive adaptations animals have, adaptations that reflect their diet.

Dental Adaptations

Let's start with probably the most obvious digestive adaptation: the teeth. Look at a cat's teeth, then look at your own, and then look inside a gift horse's mouth. You'll clearly see how different the teeth are in many respects. This isn't an accident; it reflects each animal's diet:

  • Carnivores, or meat eaters, like dogs and cats, have very large canines and pointed incisors that function to kill their prey or rip it apart.
  • Herbivores, or plant eaters, like horses and cattle, have very broad premolars and molars that allow them to grind hardy plant material down. Their incisors and canines (if present at all), are usually not as a sharp as those of carnivores.
  • Omnivores, or plant and animal eaters, like us humans, have teeth that have a mixture of carnivorous and herbivorous adaptations. We have sharp canines and incisors that help us bite and tear off flesh, but also flat premolars and molars used to grind and crush our food.

Stomach and Intestines

Like the teeth, the stomach and intestines are specialized to an animal's diet as well. For example, the stomach walls of carnivorous animals are more expandable than those of herbivorous animals. This is because carnivores may go a long time between meals and need to eat as much as possible when they have access to food. This may help explain why your dog is constantly on the prowl for food; evolutionarily, it's always concerned it may have to go a long time without food, and so it tries to fill up as much as possible right now.

On the flip side, herbivores are less likely to undergo long periods without food because plant material tends to be aplenty and, not having little legs to scatter away from the herbivores, plants are an easy victim and an easy catch for herbivores. However, the problem is that plant material is really difficult to digest. By that I mean that it's more difficult to extract all the beneficial nutrients from a hardy plant than it is from a piece of meat. So, how do you think an herbivore's digestive tract has adapted to this specific problem? Do you believe that:

A. Relative to size, an herbivore's digestive tract is longer than a carnivore's.

B. Relative to size, an herbivore's digestive tract is shorter than a carnivore's.

C. An herbivores esophagus is thicker than a carnivore's.

The answer is A. A longer digestive tract allows for plant food to remain in the digestive system for longer, allowing more time for the stomach and intestines to extract as many nutrients as possible.


All animals, be they carnivores, herbivores, or omnivores, rely on mutualistic symbiosis, a state where two dissimilar organisms live together in a mutually beneficial fashion. However, it is herbivores who rely on this process the most. This is due to the difficulty of digesting the cellulose found in plant cell walls.

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