An organism’s mouth allows it to take resources, such as food and water, into its body. In some organs the mouth serves sensory, manipulative and communication roles as well. For example, humans can detect tastes with their mouth, while animals such as dogs, birds and cats use their mouths to manipulate items. Additionally, many mammals and birds use their mouths to communicate with each other through languages and songs. Some animals use their mouths for part of the respiration process as well.
The mouths of animals vary greatly from one species to the next, reflecting its important role in the evolution of different species. An animal’s mouth is usually adapted for acquiring and processing its food. For example, carnivores have wide mouths equipped with sharp teeth, while filter-feeding whales have evolved comb-like structures to filter food from the water.
Most animals have a one-way digestive tract that features an intake — the mouth — and an exit, called the anus. However, some extremely simple organisms engage in two-way digestion, using their mouths for both the consumption of food and the elimination of waste.
Most living vertebrates have jaws that provide the structure for their mouths. The only living exceptions are lampreys and hagfish, and scientists study these creatures to help better understand the evolution of the vertebrate mouth. Scientists often call these primitive fish “living fossils” because they diverged from the rest of the vertebrates about 500 million years ago, and have changed relatively little sense then.