Question

Vertebrae in the birds are mostly
A. Procoelous
B. Heterocoelous
C. Amphicoelous
D. Acoelous

Answer 1

Hint: Vertebrae of the birds have saddle shaped ends, on one axis it is concave and on the other axis it is convex. This saddle shape is for the proper movement of the neck which allows both lateral and vertical movement.

Complete answer:
We all know what vertebrates are. In vertebrates Spinal columns or backbone are made up of a series of interlocked bones extending from neck to tail. These bones which interlock with each other to make up the spinal column are called vertebrae.

Vertebrae are divided into four types on the basis of the Centrum which means the anterior middle portion of vertebrae. There is a presence of different kinds of vertebrae in different classes of vertebrates and this feature is very common and the most defining feature of Chordates.

Like in mammals, there is presence of acoelous vertebrae i.e., vertebrae are flat from both the sides. In fishes, amphicoelous vertebrae are present as there are cavities on both the sides of the Centrum. Procoelous vertebrae are concave on the anterior side and it is convex on the posterior side of the Centrum and this is seen in the reptiles.

In Birds, heterocoelous vertebrae are present and these are characteristic of birds' necks as birds require high flexibility for the movement of their neck therefore the Centrum is saddle-shaped and hence they have heterocoelous vertebrae.

Hence, The correct answer is option (B).

Note: All the types of vertebrates possess different types of vertebrae and that also depends on different bases. The option given in the question are the types of vertebrae which are divided on the basis of the Centrum.
So, the birds have heterocoelous vertebrae since the Centrum in birds is saddle-shaped to allow the flexible motion both laterally and vertically without stretching the nerve cord.