What are the main aromorphoses that contributed to the appearance of birds on Earth?

1) The progressive development of the cerebral cortex and cerebellum led to a more complex behavior of birds
2) The appearance of a four-chamber heart with a complete separation of arterial and venous blood flow led to warm-bloodedness and intensive metabolism, as well as widespread settlement on Earth.
3) The formation of densely penetrated by capillaries lungs and the presence of air sacs allowed ventilation during inhalation and exhalation (double breathing), which is an adaptation to flight

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.