Why do fish live in the water, and what does it say about fish living in the water?

As the saying goes: fish can't live without water. It is a natural law that fish live in the water, and it is common sense that people know, so why do fish live in the water and cannot do without it?

This is mainly determined by the respirator tubes and breathing patterns of the fish itself.

One of the basic conditions for the survival of living organisms is the need for oxygen, and fish live in water and need to breathe. However, the respiratory organ of the fish is not the nose, its nostrils do not communicate with the mouth, it is a simple olfactory organ, and the gills are the main respiratory organs of the fish, which determines the difference between the breath of the fish and other land animals. The water where the fish live is oxygen-dissolved, but the dissolved oxygen is very low, and the structure of the gills is adapted to this living condition.

First, let's take a look at the structure of the gills. Now take the bony fish as an example, there are four gills on each side of the throat inside the gill cap, each gill is divided into two rows of gill pieces, each row of gill pieces is arranged by countless gill filaments, and each row of gill filaments has many gill patches on both sides, and there are many capillaries inside.

Second, let's look at the gills in the water. In the water, the gill plates, gill filaments and gill patches are fully opened, which greatly expands the contact area with the water, increases the oxygen uptake capacity of the capillaries from the water, and the fish swallows and drains water from time to time by the movement of the mouth and gill cover, and completes the gas exchange when the water flows through the gills. Therefore, the breathing movement of the fish is divided into two processes, water absorption and drainage.

When absorbing water, the operculum expands outward, the mouth and oral flap open, the operculum flap is tightly closed, and water flows from the mouth into the throat, then the operculum flap opens, the mouth and oral flap are tightly closed, the operculum moves inward, the pressure in the oral cavity increases, and the inhaled water flows through the gill fissure and is discharged from the gill hole. At this time, the carbon dioxide carried by the blood in the small blood vessels of the gills enters the water through the thin wall, and the oxygen in the water enters the small blood vessels of the gill and combines with the red blood cells in the blood, and reaches the tissue cells throughout the body with blood circulation.

Again, the density of water is much greater than that of air, it can support the gill sheets, gill filaments and gill patches of the fish completely, complete the gas exchange, once the fish leaves the water, in the air, the gill filaments and gill filaments and gill flakes will be pressed together, only the appearance of the gills and the air contact, the area is greatly reduced, and sufficient oxygen can not be obtained. In addition, the oxygen absorbed by the fish is oxygen dissolved in the water, and when the surface of the gill plates evaporates, the fish completely lose their oxygen uptake function and cannot survive. Therefore, the fish cannot live without the water, but must live in the water, which is determined by its own structure.

Of course, different fish live for different times after leaving the water, mainly because the difference in the size of the gill aperture has an effect on the rate of water evaporation on the gill piece. The slower the evaporation, the longer it will survive; On the contrary, the survival time is shorter. At the same time, it is also related to the fact that fish have other auxiliary respiratory organs, and those with auxiliary organs can survive longer after leaving the water.

This is due to the innate habits of the fish.

The fish can live in the water because it breathes with its gills, that is, it can absorb the oxygen dissolved in the water, which means that the fish cannot live on land without the water. Secondly, fish are born with the innate conditions to survive in the water.

It is originally a natural classification of aquatic animals, and living in water is adapted to the place where they grow and live.

Why fish live in water.

Summary. Hello, the fish live in the water, which shows that the fish like the water and cannot do without the water, which is mainly determined by the fish's own respiratory organs and breathing patterns. Since the respiratory organs of fish are gills, and water is denser than air, it is only in water that the gill plates, gill filaments, and gill patches of the fish can be fully opened.

By increasing the contact area between the gills and the water, the chance of taking up dissolved oxygen in the water increases the chance of obtaining more oxygen. Once out of the water, the water on the surface of the gill plates is quickly evaporated, and the fish lose the ability to take in oxygen and cannot survive. So, the fish have to live in the water.

Hello, brood fish live in water, which shows that fish like water and can't do without water, which is mainly determined by the fish's own respiratory organs and the way they breathe. Since the respiratory organs of fish are gills, and water is denser than air, it is only in water that the gill plates, gill filaments, and gill patches of the fish can be fully opened. By increasing the contact area between the gills and the water, the chance of taking up dissolved oxygen in the water increases the chance of obtaining more oxygen.

Once out of the water, the water on the surface of the gill plates is quickly evaporated, and the fish loses its ability to take in oxygen and cannot survive. So, the fish have to live in the water.

There is another reason why fish can swim fast and well. The main "swimming tool" of fish is the fin, the fin is the perfect swimming tool that the fish has evolved into after living in the water for a long time, the fish generally have a tail fin, dorsal fin, pectoral fin, and pelvic fin, of which the dorsal fin is specially used to master the balance, and the other mackerel is used to paddle and master the direction, when the fish swims, just like people use the rudder and oars when rowing, the use of various parts of the fins is very coordinated, which is easier than people walking. In addition, most of the fish are pure and sharp at both ends, and the middle is wide, which can effectively reduce the resistance of the water, and swim up to accompany the fast and light to make it loose.

Fish, like other animals, must have oxygen to survive, and most animals on land exchange gas in the lungs after breathing, so as to expel some waste gases (mainly carbon dioxide) from the body to obtain the oxygen needed for life. Fish living in water bodies do not have lungs, and their gas transfer during respiration is mainly done by gills, to be precise, small pieces of gills on the closed gill filaments. There are many gill filaments in the gill part of the fish, there are many gill filaments on both sides of each gill filament, and there are many capillaries in the gill filaments, and they are very soft, so it is necessary to rely on the buoyancy of the water to fully open, so that the contact area between the fish and the water reaches the maximum, which is conducive to gas exchange in Chunzhen.

Because people breathe with their lungs, and fish breathe with their gills.

In fact, fish, like people, must breathe oxygen to survive, there is oxygen in the air and water, and the human lungs can separate the oxygen in the air but cannot take the oxygen in the water from the bucket ruler, so people can only live on land.

And can't breathe in the water, most fish don't have lungs.

But there are gills that separate oxygen from the water.

So, the fish can breathe oxygen in the water.

There are also some fish, in addition to gills and lungs.

So talk about those fish can live on land for a while.

Some of them can live for a few hours, some for a few days, and some even on land for years.

About the structure of the fish, see the following.

**Illustrate. It's intuitive:

Fish in the river in winter in deep water.

If the water is relatively wide, the fish want to winter, most of the water color is darker and turbid, even if the winter activity is poor, but it is not motionless, the fish will gather together to have a sense of security, so at this time the water body is turbid most likely to have fish underwater. In winter, the temperature is relatively low, and the fish tend to be in some sunny places. Fish basically don't like to swim around, so you can choose some sunny places, ** the high water temperature, the more activities the fish will be.

The temperature of the water is related to the density of the water, and at a certain temperature, the deeper the depth, the higher the water temperature. Of course, at the same depth, the higher the temperature, the higher the water temperature.

4 degrees Celsius water is the most dense, so 4 water is at the bottom and 0 is the same as ice, and at the top is deeper. Therefore, as long as the pond is not completely frozen in winter, the fish can survive, and the fish can move in the water for 4 years.