The respiratory system of birds has unique structures that cause fresh air to flow into the lungs in only one direction , a capacity that allows them to cope with the large amounts of energy required by flight. At least that is what supports the most widespread hypothesis among zoologists. However, a team of researchers from different US institutions has discovered that green iguanas, reptiles that do not usually display intense physical activity, have developed a similar adaptation.
Biologist Collen Farmer, from the University of Utah, who coordinated the study, points out that the finding suggests that the unidirectional respiration present in modern birds evolved long before its appearance, probably from a common ancestor to them , dinosaurs. non-avian crocodiles, snakes and lizards about 300 million years ago.
The airways of humans and other mammals resemble a tree : when we inhale, the air flows through the trachea and divides into the bronchi over and over again until it reaches the alveoli. In addition, it is bidirectional, since when we exhale it, it follows the opposite path. On the contrary, the air sacs of birds, exclusive organs of these animals, accumulate air and release it each time they breathe in and out.
As they are connected to the lungs, they receive air in only one direction and make better use of oxygen. Although this process was believed to be related to the ability to fly, Farmer and his colleagues have challenged this assumption in an article published in the journal Proceedings of the National Academy of Sciences.
In fact, this expert, in collaboration with other scientists, had already found out in 2010 that alligators also have a unidirectional system, like monitor lizards . In his opinion, all this indicates that the same biological design was formed from independent evolutionary processes.
