BIRDS

BIRDS

These animals we distinguish them easily because they are the ones with feathers. Actually feathers are what scientists use to decide whether an animal is a bird or not. If you have pens is a bird. If you have pens then it is not a bird. Only birds have feathers, and all species of birds have feathers.
Like the reptiles, amphibians, mammals and fish, birds are vertebrates. It just means they have skeleton vertebrae. In contrast to other animals such as insects, sponges, sea stars and many others. Some of these other animals have skeletons, but is a different skeleton.
The birds are descended from reptiles. About 200 million years ago, the scales were developed feathers, thus emerging the first bird. It is estimated that there are about 9,700 different species around right now.

The birds that exist today are studied in two basic groups. Those that can fly and who have lost the ability to do so. These last ones called ratites or brokers. Among the ratites have ostrich, rheas, cassowaries and others. To the surprise of many, the flying (also called keeled) penguins are included, as although not fly through the air, they do in the water. And along with penguins, are the vast majority of the rest of the birds we know.