Question

What is the rudimentary eye? Explain with examples.

Answer 1

Hint: The eye is an example of an analogous organ found in many animal forms. Simple light detection is found in bacteria, single-celled organisms, plants and animals. Complex, image-forming eyes have evolved independently multiple times. The earliest known fossil of complex eyes is from the Ediacaran, with the appearance of the stem mollusc Clementechiton sonorensis.

Complete answer:
Eyes vary in their visual acuity, the range of wavelengths they can detect, their sensitivity towards low light, their ability to detect motion or to resolve objects, and whether they can discriminate various colours.

Light entering the eye is refracted as it passes through the cornea which then passes through the pupil that is controlled by the iris and is further refracted by the lens. The cornea and lens act together as a compound lens in order to project an inverted image onto the retina.

Rudimentary eyes are undeveloped eyes. The examples of rudimentary eyes are the reduced size of the eyeball or eyeball may be absent, complex iris, rudimentary cornea and other underdeveloped features. Planaria has rudimentary eyes.

The earliest predecessors of the eye were photoreceptor proteins that sense light, present in unicellular organisms, called eyespots. Eyespots can sense only ambient brightness which means they can distinguish light from dark, sufficient for photoperiodism and daily synchronization of circadian rhythms. They are insufficient for vision because they cannot distinguish shapes or determine the direction light is coming from.

Note: The visual system comprises of the sensory organ which is the eye and parts of the central nervous system which consists of the retina containing photoreceptor cells, the optic nerve, the optic tract, and the visual cortex which gives organisms the sense of sight that means the ability to detect and process visible light as well as enabling the formation of several non-image photo response functions.