Wednesday, March 25, 2009


Birds are winged,bipedal,endothermic vertebrate animals that lay eggs.There are around 10,000 species making them the most numerous vertebrates.They inhabit ecosystems through the globe,from Arctic to Antarctic. They range in the size 5cm(Bee Humming Bird)to 2.7m(Ostrich).Their fossils recorded that birds evolved from dinosaurs during the Jurassic period.The earliest bird known in the Late Jurassic is the Archaeopteryx.Paleontologists regard birds as the only dinosaurs that survived during the Cretaceous period from the extinction event.

Modern birds are characterised by feathers, a beak with no teeth, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton.All kinds of birds have forelimbs.

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