Question

Pecten is a structure found in the eyes of
A. Reptilia
B. Fish
C. Birds
D. Mammals

Answer 1

The eyes are one of the most important and vital sensory organs that are present in the living organism. In lower organisms, it is present in the form of sensory light sensitive structure while in higher organisms, it develops into a complex ocular light sensory structure.

Complete answer:
Eyes are developed from simple light sensitive photoreceptor cells that are sensitive to frequencies of light. In higher organisms, especially in all the vertebrates, the structure of the eye is more or less similar but each one is adapted to the environment to which the animal is subjected to.
In birds, the basic structure of the eye is similar to other vertebrates. However, they bear some adaptations that provide them with higher vision acuity than other organisms. In birds, some external specialized features are the size of the eyeball, presence of a third transparent movable membrane and internally, it contains a unique structure known as the pecten oculi.
Pecten oculi is a comb like structure made up of blood vessels that belongs to the choroid in the bird’s eye. It is a pigmented, non-sensory structure and it projects into the vitreous humor at the point of entry of optic nerve. The optic nerve enters the eye ball. The main function of the pecten is to provide nourishment of the retina and regulating the pH of the vitreous body. Pecten also helps to reduce the number of vessels which in turn increases the sharp eyesight of the birds.
In reptiles, the eye is variably developed and in some cases, it has developed nocturnal vision. In some species, eyelids are not present while some species the eyes can rotate in almost every direction.
In mammals, the eyes are sensitive to light and contain eyelids. Eyes in mammals do not contain pecten.
In fishes, the eyes have a more spherical lens and the retina contains both rod cells and cone cells. It does not bear any eyelid. Pecten is not found in the eyes of fishes.
Thus, the right option is C.

Note: The eyes are related to the function of vision in higher organisms and are evolved to assist the organism to become more aware of the surroundings in order to survive. In birds, vision is important for their survival and the eyes contain some specific adaptations. The eyes of birds contain a comb-like structure which is known as the pecten oculi or pecten.