Question

Which of the following vertebra is an amphicoelous type of frog?
A. ${3^{rd}}$
B. ${8^{th}}$
C. ${9^{th}}$
D. ${10^{th}}$

Answer 1

Hint: Vertebrae constitute the vertebral column. The animals which possess the vertebral column are called vertebrates. The vertebra is a bony structure of irregular shape. The size of the vertebra varies according to their position in the vertebral column. The end surfaces of these structures are different in different groups of vertebrates.

Complete answer:
Vertebrae constitute the vertebral column. It is a bony structure whose articulation gives rise to the formation of the column. Each vertebra is bony and irregular. the structure of a typical vertebra is described below:
-An anterior body.
-Posterior bony projections and processes that function as points of articulation – with neighbouring vertebrae and with muscles and ligaments.
-A central foramen. The vertebrae are stacked one on top of each other and the central foramen forms a canal through which the spinal cord passes and connects to the brain.
-The end surfaces of a vertebrae show concavities in varied degrees. The anterior parts are generally more concave than the posterior parts.

The end surfaces of each vertebrae are shaped in a specific way in each vertebrate class. This shape is constant in animals of the class and helps us to identify the clade and class of fossilized organisms. based on this shape of the end surfaces, vertebrae can be of five types:
Procoelous: vertebrae that have a concave anterior end only. Frogs and reptiles have procoelous vertebrae. Amphicoelous: vertebrae that have concave ends. Salamanders have amphicoelous vertebrae. Opisthocoelous: vertebrae with a concave posterior end only. Acoelous: vertebrae with flat ends. Mammals belong to this group. Heterocoelous: vertebrae that are convex on one axis and concave on the other. The free neck bones of birds have heterocoelous vertebrae.
The vertebral column of frogs is unique. It is highly reduced. The number of presacral vertebrae is 9. The sacrum has only one vertebra with very stout transverse processes. Since the frogs respire through buccal pumping, ribs are generally absent. The first vertebra is cervical. Second to seventh is of procoelous type. The eight vertebra is of amphicoelous type, while the ninth one is biconvex and attached to the urostyle.

Hence, the correct answer is option (B).

Note: The vertebral column is an axis that protects the spinal cord, provides a place for attachment of nerve roots, muscles and supports the trunk. The vertebral column is composed of small bony structures called vertebra. Vertebral column of frogs is reduced. The eighth vertebra is of amphicoelous type.