Question

Which of the following is a characteristic feature of the bones of the birds?
A. Four chambered heart
B. Pneumatic bones
C. Hollow nerve cord
D. Large eyes

Answer 1

‘Pneumatic relates to air'. The term pneumatic bones refer to air-filled bones. A four-chambered heart has two atriums and two ventricles. The ventricles are smaller upper chambers. The ventricles are the lower larger chambers. A hollow nerve cord is a hollow tube of ectoderm derivative found in all the vertebrates. It develops from the notochord in the form of an empty tube.

Complete answer: The bones of birds are designed hollow. These are known as pneumatic bones. The pneumatic bones are associated with the respiratory system of the bird. These enable birds to breathe with ease. The pneumatic bones are an important element of the respiratory system of the birds. Some of the pneumatic bones are the skull, sternum, clavicle, sacrum, and lumbar vertebrae. These are the bones with air spaces. Not just respiration but these air-filled bones also allow the birds to fly freely by reducing the weight of the body. Thus, they provide buoyancy to the bird easing out its flight. Birds also have hollow nerve-cord which is a characteristic of all vertebrates. They also have a four-chambered heart and bigger eyes if compared with the mammals.
Thus the correct answer is option (B) pneumatic bones.

Note: Humans also have pneumatic bones. For example mastoid process of the temporal bone, maxilla, ethmoid, and sphenoid. Not all birds have pneumatic bones. The birds that dive into water lack pneumatic bones. Sometimes, bones can become pneumatic also due to some pathological happenings.