You also know I love with birds. I want to share some amazing birds with you. You also like it.
Today I tell the history of evolution of birds.
Birds are a group of warm-blooded vertebrates constituting the class Aves, characterized by feathers toothless beaked jaws, the laying of hard shelled egg,a high metabolic rate four chambered heart,and a strong yet lightweight skeleton. Birds live worldwide and range in size from the 5cm bee hummingbird to the 2.75 ostrich. There are about ten thousand living species, more than half of which are passerine,or perching birds. Birds have wing whose development varies according to species, the only known group with out wings are the extinct moa and and elephant birds.
Wings, which evolved from forelimbs,gave birds the ability to fly, although further avolution has led to the loss of flight is some birds including ratites,penguins,and diverse endemic island species. The digestive and respiratory systems of birds are also uniquely adapted for flight. These pictures are takon from Google.
