bats and birds

Bats and birds both fly, but a bat is not a bird. So how do you tell them apart?


If we look at the red corpuscles of a bat under a microscope, we'll find that they don't have nuclei.

On the other hand, birds' red corpuscles do.

This proves that bats are mammals - more evolved, mammals have more efficient corpuscles. Nuclei take up space, precious space that can be filled with the red pigment haemoglobin which carries the oxygen. Red corpusles in mammals are totally filled with haemoglobin.

This is further proof that birds are descended from reptiles, which also have nuclei in their red corpuscles.