By Alessio, I°A
By Alessio 1A
All birds are vertebrates. They have a backbone that acts as the framework for central nervous system. Bird have a four-chambered heart, but their hearts beat much faster than ours do and their metabolic rate is much higter because flying expends enormous amounts of energy. Birds bodies also have air sacs that trap oxygen in the body to circulate it through the lungs and bloodstream for longer.
Like our human hearts, a bird 's heart is divided into four chambers and serves to pump oxygen-rich blood throughout the body. Because birds are such high-energy animals, their of over 500 beats per minute!
The average human heart beats at 72 beats per minute, the sparrow's heart at 460 and the tiny hummingbird at 615 beats per minute!
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