Explain how birds have adapted themselves to an aerial mode of life.

Explanation

1. The body is covered with feathers.
2. The feathers are attached to forelimbs.
3. The bones are hollow and light and called pneumatic.
4. The presence of a single right ovary.
5. The breast bone called keel is provided with powerful flight muscles.
6.The lungs are associated with air sacs to increase the capacity of inhalation. Lungs are inelastic.
7. The bones have fixed structures so that while flying the bones never dislocate.
8. Body streamlined.
9. The beak is without teeth.
10. Gizzard is present,
11. Gall bladder and urinary bladder are absent.