The first birds evolved from reptiles. Like reptiles they had teeth. Modern birds have no teeth and the bones of the skull and beak have air spaces inside them.

The drawings show a reconstruction of the skeleton of a fossil bird and the skeleton of a modern pigeon.









Suggest why it is an advantage to modern birds to have air spaces inside the bones and beak.

Explain as fully as you can, how birds have evolved air spaces inside their bones and beak as a result of Natural Selection (5-8 marks)