In zoology, the main characteristics of birds are: their bodies are streamlined (spindle or fusiform), and most of them fly. The body surface is covered with feathers, and the forelimbs usually turn into wings (some species have vestigial wings); the chest muscles are well developed; the rectum is short, and the food intake is large and the digestion is fast, that is, the digestive system is developed, which helps to reduce weight and facilitate flight; the heart has two atria and two ventricles. , the heart rate is fast. Body temperature is constant. In addition to the lungs, the respiratory organs also have air sacs formed by the protrusions of the lung walls to help the lungs perform dual breathing. The following is a simple drawing of a bird brought by the editor. I hope it will be helpful to you.
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