Any living organism is an ideal system, and if the circulatory, nervous and other organ systems allow us to exist, then the sensory organs are just what the body learns and perceives of the external environment. Moreover, each class of animal organisms has its own characteristics.
Sensory organs of fish
Representatives of this class of animals have rather developed eyes, which consist of the retina, lens and cornea. The fundamental difference between these organs is that when the image is perceived, the lens does not change the curvature, as in other vertebrates, it simply moves relative to the cornea, thereby focusing the eye.
There are fish and hearing organs, which are three semicircular, mutually perpendicular channels. Some representatives also have the so-called Weber organ, which connects the cavity of the inner ear with the swim bladder, which in this case works as a sound resonator. Receptors that perceive taste and smell can be located not only in the oral cavity and nostrils, but also scattered throughout the body.
Another interesting organ is the lateral line, which is a collection of channels connected to nerve fibers. The lateral line is especially developed for those fish that do not have eyes - it is thanks to it that they can perceive the outside world and maintain balance.
It's no secret that some fish can respond to electric fields and even generate electrical impulses using special cells and nerve fibers.
Amphibian sensory organs
The sensory organs of representatives of this class are already more adapted to existence in the air. For example, their eyes already have eyelids, as well as a blinking membrane, which performs moisturizing and protective functions. The lens can change its size depending on the lighting.
In addition, amphibians have olfactory sacs that open outward through the nostrils. An animal can only smell in the air. As for the hearing organs, amphibians have already formed the middle ear and the eardrum, as well as a small bone called the stapes.
All mechanical receptors are located in the skin tissue. In primitive aquatic amphibians, as well as in tadpoles, a lateral line is still preserved.
The sensory organs of reptiles
Representatives of this class sense organs are already more developed and adapted in life in the air. Very important for these animals are the eyes, which are more shaped than amphibians - there are developed muscles that attach to the lens and can change its curvature to focus the image. In addition, reptiles have real lacrimal glands, the secret of which protects the animal’s eyes from drying out. There are moving eyelids.
Such animals have choanas (inner nostrils), which are located closer to the pharynx, which greatly facilitates breathing during meals. It is proved that reptiles are much more sensitive to odors than representatives of the amphibian class.
The taste organs are represented by specific structures - taste bulbs, which are located in the throat. And between the eyes and nose is the so-called facial fossa, which allows you to respond to temperature changes. For example, in some snakes, it is this organ that allows you to quickly find food.
Hearing organs are not very well formed and resemble amphibian hearing aids. Reptiles have a middle and inner ear with an eardrum, as well as a stapes - a small bone that transfers vibrations to the eardrum. Hearing in the life of these animals is not particularly important. For example, in snakes it is practically not developed.
As you can see, the senses gradually changed during evolution, adapting to survival under certain conditions and becoming more complex and functional.