Question

Describe gas exchange in a bird’s lung. (Be comprehensive.) How is gas exchange in a bird’s lung similar to gas exchange in a fish’s gill?

Answer 1

Birds respiratory system consist of a pair of lungs , with connected air sacs (expand and contract ) structures which are static for surface gas exchange , As bird's don't have diaphragm air is moved in and out of respiratory system on basis of pressure changes in air sacs .Sternum is pushed outward by chest muscles. Gas exchange occurs through microtubules capillaries .Flying consumes a huge  amount of energy; therefore, birds require a lot of oxygen to aid their metabolic processes.

As bird first inhales air flows into the posterior air sacs and partly into the lungs . As bird first exhales air from the posterior air sacs is forced into the lungs,. In case of second inhalation air from first inahalation moves into anterior air sacs and partly into the lungs. Air from second inhalation flows into the posterior sacs. Second exhalation most of air from first inhalation leaves the body and air from the second inhalation flows into lungs. It is process of one way air flow

SIMILARITY :Fishes posses swim bladder and birds posses airsacs to maintain buoancy. Only in fish gills and in avian lungs might a substantial overlap of gas blood andPO2 and or PCO2 occur.