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Birds are the only animals with feathers, although some bats and insects have wings. Nearly all birds can fly and even flightless birds such as penguins and ostriches evolved from flying birds. Like mammals’ birds have 4-chambered hearts and are warm-blooded, however like reptiles birds develop from embryos in eggs outside the mothers body. ... These adaptations reduce a birds’ body weight and make the body more compact. ...
Birds have this skin covered with feathers. ... Some of the bones that make up joints in reptiles and mammals are fused in birds. ...
Birds generate and maintain a constant internal body temperature. Birds can live in very cold climates, where reptiles cannot survive, because they are endothermic. The overlapping feathers of birds trap air and minimize the loss of body heat. ... That is why birds have a more efficient respiratory, circulatory, and digestive system than reptiles. ...
Birds must eat and digest large amounts of food to provide enough energy for flight and for generating body heat. When birds eat the unchewed food passes through the esophagus. ... The excretory system of birds is adapted to conserve water from the body wastes. ... Birds do not have a urinary bladder in which to store liquid wastes.
Approximate Word count = 963
Approximate Pages = 3.9
(250 words per page double spaced)
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