Question

Pinna or external ear is found in
A. Insects
B. Aves
C. Reptiles
D. Mammals

Answer 1

Hint: There are various classes which belongs to kingdom animal. The major traits
inherited by all the living mammals are jaw joint, middle ear, tooth replacement, prismatic enamel, and
occipital condyles.

Step by step answer:Ear is a characteristic feature of mammals. The ear can be further
distinguished further into 3 parts: the outer ear, middle ear, and inner ear. The external organ called
auricle or pinna and ear canal (auditory canal) forms the outer ear. The auditory canal terminates, with
the tympanic membrane (eardrum) in the inner side of the ear. The function of the outer ear is to
collect the external sound waves and transmit them to the tympanic membrane. The middle part of the ear comprises of three bones and a narrow cavity filled with air in the temporal bone called a tympanic
cavity. Malleus, incus, and Stapes are the three bones present in the middle ear. These bones are
collectively known as auditory ossicles. They are the smallest bone found in the human body. The inner ear consists of two parts: bony labyrinth comprising of the vestibule, semicircular canals, cochlea, and
membranous labyrinth which consists of the utricle, saccule, semicircular ducts and cochlea ducts. The oval window is responsible for the communication between the vestibule and the tympanic membrane. The cavity spaces of the membranous labyrinth are filled with a fluid called endolymph. It is responsible for maintaining the pressure and balance of the body.
Hence option D is correct.

Note: The external ear is a characteristic feature of mammals, but it is absent in some aquatic animals for example whales. It is divided into three main parts an outer, middle, and an inner part.