Biology » Vertebrates » Birds

Summarizing Birds


Birds are endothermic, meaning they produce their own body heat and regulate their internal temperature independently of the external temperature. Feathers not only act as insulation but also allow for flight, providing lift with secondary feathers and thrust with primary feathers. Pneumatic bones are bones that are hollow rather than filled with tissue, containing air spaces that are sometimes connected to air sacs. Airflow through bird lungs travels in one direction, creating a cross-current exchange with the blood. Birds are diapsids and belong to a group called the archosaurs. Birds are thought to have evolved from theropod dinosaurs. The oldest known fossil of a bird is that of Archaeopteryx, which is from the Jurassic period. Modern birds are now classified into two groups, Paleognathae and Neognathae.



transition species from dinosaur to bird from the Jurassic period

contour feather

feather that creates an aerodynamic surface for efficient flight

down feather

feather specialized for insulation


dominant bird group during the Cretaceous period

flight feather

feather specialized for flight


wishbone formed by the fusing of the clavicles


birds other than the Paleognathae


modern birds


ratites; flightless birds, including ostriches and emus

pneumatic bone

air-filled bone

primary feather

feather located at the tip of the wing that provides thrust

secondary feather

feather located at the base of the wing that provides lift


dinosaur group ancestral to birds

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