Why do animals have two nostrils? 0 11

Despite the small distance between the nostrils, their separation allows for more precise localization of the source of a smell. Overall, the bodies of most animals exhibit bilateral symmetry, which makes the formation of paired organs easier than that of unpaired ones. Thus, olfactory organs developed on both sides of the anterior end of the neural tube.

Therefore, even in the earliest fish, nostrils became paired, and this trait has been preserved in vertebrates. With the transition of animals to land, nostrils transformed into breathing openings; however, the olfactory function remained.

Nevertheless, not all animals have two nostrils. In toothed whales, the breathing opening is formed only by the left nostril, while the right has become blocked and lost its connection to the external environment.