Basic definition: the general name of vertebrate subfamily birds. Oviposition, constant body temperature, covered with feathers. The front legs become wings and can fly; The hind limb is the foot, which is used for walking or standing. There are no teeth in your mouth. Breathe with your lungs. Most birds can fly, but some can't, such as chickens, ducks, geese and ostriches. There are many kinds, all over the world.
The sound of birds. -"Xiao Yi Guo"
I don't listen to birds. -"Shu Jun Xuan"
Birds fly high. -"Poetry Xiaoya Liu Liu"
Birds are a subclass of vertebrates, which is the general name of all birds and animals. The body is streamlined and the skin is thin and elastic; The body is covered with feathers, generally the forelimbs become wings, and some kinds of wings degenerate; The pectoral muscles are developed; Short rectum; The heart has two atria and two ventricles, and its temperature is constant.
Birds are distributed all over the world. Most birds move during the day, and a few birds move at dusk or at night. It can be divided into carnivorous, fish-eating, insect-eating and phytophagous types, and there are also many intermediate and omnivorous types.
The origin of birds
The research on the origin of birds has gone through several stages. 1868, Huxley put forward the hypothesis that birds originated from dinosaurs. Huxley is a famous British biologist and a staunch supporter of Darwin's theory of evolution. At the same time, he was also the first scholar to put forward the theory that birds originated from dinosaurs.
1927, Danish paleontologist Hailmann published a very classic book "The Origin of Birds" in his 1927, in which he pointed out that although birds and dinosaurs are very similar, dinosaurs have been very specialized, so birds may not have originated directly from dinosaurs, but have a * * * ancestor with dinosaurs, that is, teeth.
The so-called Serrat is a more primitive fossil group than dinosaurs. This group is considered as a large group, which has produced some major modern vertebrates, such as dinosaurs, birds and crocodiles. It may have appeared earlier than Jurassic and Cretaceous in Triassic.