It may seem surprising, but all the animals, people, birds, fish and insects have the same internal organs and may equally feel heat, cold, hunger, and pain. This leads scientists to believe that they are all evolved from a single ancestor.
Despite the fact that fish are cold-blooded animals, their internal structure is very similar to the structure of the higher warm-blooded animals. Fish breathe and digest food. They have a nervous system, they are also feeling the pain, smell, taste, feel uncomfortable, if it gets too cold or hot.
Fish have two pairs of nostrils, located on the head, besides each nostril has two openings. When the fish swims, the water flows into the front nostril and flows out through the rear, provoking sensitive cells, which tell the fish all information about the smell.
Fish have ears, but they are located inside the head, not outside, as we used to see. So the fish hear very well and in case of danger immediately swim away.
Fish can feel pain, heat and cold with sensitive cells, which are located all over the body. Taste they also fell with entire body.
When you’re looking at your fish in the aquarium, you may find it strange that they never close their eyes and do not blink. This is because fish do not have eyelids.
Fish can be blinded by bright light, because their eyeballs are not narrow, as humans eyeballs and can’t reduce the ray of light passing through eyeballs.
Fish never cry because they have no lachrymal glands. But they do not need them, because fish are constantly in water that bathes their eyes, and they do not dry up. For all other indications the eyes of fish and other animals are very similar. They also have the iris surrounding the pupil. Scientists conducted experiments with fish and have proved that they can distinguish color: can distinguish red from green, blue from yellow. Besides, fish can see more than people, because their eyes are located on either side of the head. Despite the fact that each eye sees all on only one side, with both eyes fish can see very well and notice the slightest movement.
Fish breathe interesting too. They swallow water with mouth, water passes through the gills and poured through a special opening.
From swallowed water through the gills oxygen enters the bloodstream, just like humans, it enters the bloodstream through the lungs.