Circulatory System
Birds have a four-chambered heart, in common with humans, most mammals, and some reptiles (namely the crocodilia). This adaptation allows for an efficient nutrient and oxygen transport throughout the body, providing birds with energy to fly and maintain high levels of activity. A Ruby-throated Hummingbird's heart beats up to 1200 times per minute (about 20 beats per second).
Read more about this topic: Bird Topography
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“New York is more now than the sum of its people and buildings. It makes sense only as a mechanical intelligence, a transporter system for the daily absorbing and nightly redeploying of the human multitudes whose services it requires.”
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