Respiratory system of vertebrates. Its complications in the process of evolution.

In fish, the respiratory organs are gills (networks of thin gill petals). In amphibians, breathing through the skin and with the help of the lungs, which look like bags with thin walls. Reptiles breathe only with the help of their lungs, which have a network of partitions and many cells. Birds have spongy lungs with highly branched bronchi and pulmonary sacs. The respiratory system reached its greatest development in mammals. It is represented by the lungs with the smallest vesicles – alveoli.