![]() ![]() Archaeopteryx and Xiaotingia, for example, were flying dinosaurs and are believed to be early precursors of birds. In fact, fossil evidence shows that meat-eating dinosaurs that lived more than 100 million years ago had a similar flow-through respiratory system with lungs and air sacs. How did birds evolve a respiratory system that is so unique?ĭecades of research by paleontologists have shown that birds evolved from therapods, meat-eating dinosaurs ( Figure). Furthermore, many birds fly in high altitudes where the concentration of oxygen in low. Flying is a high-energy process and requires a lot of oxygen. Evolution Connectionīirds have evolved a respiratory system that enables them to fly. This directionality of airflow requires two cycles of air intake and exhalation to completely get the air out of the lungs. This type of breathing enables birds to obtain the requisite oxygen, even at higher altitudes where the oxygen concentration is low. The flow of air is in the opposite direction from blood flow, and gas exchange takes place much more efficiently. Air flows in one direction from the posterior air sacs to the lungs and out of the anterior air sacs. In addition to lungs, birds have air sacs inside their body. The details of breathing between birds and mammals differ substantially. Oxygenated air, taken in during inhalation, diffuses across the surface of the lungs into the bloodstream, and carbon dioxide diffuses from the blood into the lungs and expelled during exhalation. Similar to mammals, birds have lungs, which are organs specialized for gas exchange. Birds have evolved a respiratory system that supplies them with the oxygen needed to enable flying. Flying consumes a great amount of energy therefore, birds require a lot of oxygen to aid their metabolic processes. To aid this diffusion, amphibian skin must remain moist.īirds face a unique challenge with respect to breathing: They fly. The other means of breathing for amphibians is diffusion across the skin. Adult amphibians are lacking or have a reduced diaphragm, so breathing via lungs is forced. ![]() These lungs are primitive and not as evolved as mammalian lungs. As the tadpole grows, the gills disappear and lungs grow. Young amphibians, like tadpoles, use gills to breathe, and they donât leave the water. ![]() Amphibians have evolved multiple ways of breathing. ![]()
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