Emerald Robinson: Hi! I am Emerald Robinson, and in this What is video, we will examine natures plant eaters, herbivores. An herbivore is an organism that exclusively eats plants for its diet. Herbivores are heterotrophs; which means they cannot make their own food and need to get nutrition by eating other organisms.
Herbivores are also primary consumers because they eat organisms that are able to make their own food, namely plants and algae. The role of herbivores in a food web is extremely important. Herbivores are able to break down a carbohydrate called cellulose, the major component of plant cell walls. As herbivores are eaten by other consumers, the energy from this carbohydrate is passed into higher levels of the food web. Herbivores have many adaptations that enable them to eat and digest plants. Many herbivores have teeth in the front of their mouth made to bite or snip off vegetation and very large ridged molars on the back of their jaw that are used to grind plant matter for swallowing. Once the plant is swallowed, the tough cellulose molecule must be broken down so it can be absorbed. Ruminant herbivores like cows and sheep spit up or regurgitate partially digested food from their specialized stomachs to chew again. This process is called Chewing Cud. The cud is re-swallowed and its cellulose broken down by enzymes, manufactured by bacteria that live in the herbivores lower digestive system. Non-ruminant herbivores like horses and rabbits break down cellulose in a large and complex large intestine. These herbivores spend about 75% of their time grazing, because so much nutrient rich but indigestive plant matter by-pass the small intestine where nutrient absorption takes place. Although some human choose to eat only plants, they are not scientifically speaking herbivores. All humans are by definition omnivores, because they are able to digest both plant and animal tissue.