How fish breathes?
Hundreds of thousands of years ago, long before the appearance on Earth of man, the oceans already swam fish. At that time they were the most highly developed creatures.
Since then, they began to develop a variety of ways so that now only some species only vaguely resemble the first primitive ocean fishes.
As a rule, fish has an elongated and tapering shape. People have copied it in the construction of ships and submarines, as it is the best adapted to movement in water.
Most fish use their tail as a motor. With the help of fins and they control their movements. Except for one species of fish, all the others breathe by means of gills. Fish swallows mouth water that passes through the gills and out through the hole. Water also contains oxygen, and it through the gills into the blood of fish, as the air through the lungs in the blood of man.
In polluted water the fish are trying to float to the surface and breathe air, but their gills are not adapted to the absorption of oxygen from the air.
The blood of fish is cold, but their nervous system is the same as
Fish can smell. They have two small scent organ located in the nose on the head. Do fish have ears, but they are inside heads and are called “inner ears”. The reason that fish have dark coloration on top and light bottom, is that it helps them to protect themselves from their enemies, which, viewed from above, you see a dark color, merging with the water of the river or ocean. Looking from below, it seems that this bright surface of the water. There are more than 20 thousands of fish, and it’s hard to imagine, how unique is life in each!
Does the fish heart?
Sometimes it is very difficult to imagine that beings us it is not similar can have the organs, and very reminiscent of our functioning about the same. Many people think that because a fish lives in water and has cold blood, then it must be missing various internal organs or emotions.
In fact, the internal structure of fish is very similar to the structure of the higher, warm-blooded animals. Many scientists believe that this similarity proves that life on land emerged from the sea!
Fishes breathe and digest food. They have a nervous system, they feel pain and physical discomfort. They have a very developed sense of touch. They have taste sensations, and very sensitive skin. They have two small organ of smell in the nostrils, located on the head. Even the ears they have, but they are inside the body of the fish. The external organs of hearing in fishes is not. The eyes in fish are the same as in vertebrates of other species, but have a simpler structure. Thus, you can see that fish there are “systems” that allow it to perform functions similar to functions of our body. Let’s take a brief look at just two of these systems — digestion and blood circulation. The fish food passes through the esophagus into the abdominal cavity, where the gastric glands and where digestion starts. Then it passes into the intestine where is absorbed, is absorbed into the blood. Different kinds of fish have different digestive systems that are adapted to different types of food — from vegetable to other fish.
But he uses food the fish with the same goal that we do: as a source of energy for life, growth and movement. The circulatory system of fish carries food and oxygen to all the internal organs. Pump, regulating the circulation of the fish, like humans, is the heart. Heart fish gills located behind and just below them. It has three or four cameras, which, as we have steadily reduced.
There are thousands of different species of fish, each of which is adapted to certain living conditions, but their internal organs, senses and systems similar to our own.