Why do fish swim in the water 10, why do fish swim in the water

Fish, like humans, must breathe oxygen to survive, there is oxygen in the air and water, and the lungs of humans can separate the oxygen in the air but cannot absorb the oxygen in the water, 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 those fish can live on land for a while.

Some of them can only live for a few hours, while others can live for a few days.

Others can even live on land for a few years.

Fish have the characteristics of being suitable for living in water: the color of the body of the fish is the protective color of the fish. The body is streamlined, large in the middle and small at the end.

The surface of the body is covered with scales, which protect the body; There is a layer of mucus on the surface of the scales, which reduces the resistance of the water when swimming. There is a lateral line on both sides of the body, which is connected to the nerve, which is mainly used to determine the direction and sense the flow of water. The body of a fish has pectoral fins, dorsal fins, pelvic fins, and caudal fins, which are the locomotor organs of the fish in the water.

Fish breathe with gills. There is a swim bladder in the body, the main role is to regulate the specific gravity of the body, the swim bladder in the coordination of the fins, can make the fish stay in different water layers.

Fish belong to the lower animals of vertebrates because they cannot live without water all their lives, breathe with gills, heart-atrium-ventricles, a circulatory route, and arterial and venous blood are mixed; In particular, the reproduction of fish is naturally hatched by in vitro fertilization, and the body temperature is not constant.

The role of the fin: The dorsal and anal fins mainly play a stabilizing and balancing role when moving. The tail fin works with the muscles on the side of the body to propel the fish and control the direction.

The main function of pectoral and pelvic fins is to maintain the balance of the fish, cooperate with the body of the fish, and adjust the lifting of the fish. However, pectoral fins are more versatile than pelvic fins, and they can be used like oars to move the fish forward slowly.

Because the gills of a fish are only adapted to absorb oxygen from the water and cannot absorb oxygen from the air, it can only live in the water.

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 absorb the oxygen in the water, 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 those fish can live on land for a while.

Some of them can only live for a few hours, while others can live for a few days.

Others can even live on land for a few years.

About the structure of the fish, see the following.

**Illustrate. It's intuitive.

For there are cats on the earth and birds in the sky.

The reason why fish can swim in the water is related to the physiological structure and living habits of the fish.

1. Fish bladder. : By adjusting the air capacity inside the swim bladder, the fish can float and sink freely in the water.

2. Fish tail: can control the direction of swimming.

3. Fins. : It is the driving force for progress.

4. The gills of fish: can absorb oxygen dissolved in water without drowning.

5. The shape of the fish: The body shape of the fish is more suitable for living in the water and has less resistance to the water. Therefore the fish can swim.

Fish mainly breathe through the gills, and the water flows in from the mouth and out of the gill holes, and the gas exchange is constantly carried out through the gills, hence the gills.

It has a special structure.

Fish mainly breathe through the gills, and the flow of water flows in from the mouth and out of the gill holes, and the gas exchange is carried out as it passes through the gills. Therefore, the gills have a special structure. Fish generally have 5 pairs of gill arches, the inner edge is the gill raker, the outer side of the two ratios of gill plates, the gill is composed of countless gill filaments arrangement, each gill filament and many protruding gill pieces, the gill filaments are composed of 2 cells, with abundant microvessels, is the place where gas is exchanged.

Fish mainly breathe through the gills, and the flow of water flows in from the mouth and out of the gill holes, and the gas exchange is carried out as it passes through the gills. Therefore, the gills have a special structure. Fish generally have 5 pairs of gill arches, the inner edge is the gill raker, the outer side of the two more than the gill piece, the gill is composed of countless gill filaments arrangement, each gill filament and many protruding gill pieces, the gill filaments are composed of 2 cells, with abundant microvessels, is the place of gas exchange.

The adjacent ones are staggered with small gills in which water flows to ensure maximum gas exchange between blood and water. When the fish leaves the water, the gill filaments and gill pieces are adhered to each other, the breathing area is greatly reduced, and sufficient oxygen can not be supplemented, and the gill filaments are exposed to the air, and the gill filaments are dry due to the evaporation of water, which destroys the structure of the gills and makes them lose their respiratory function and die.

Because the fish belongs to aquatic life, its gills can filter out the oxygen in the water, so that it can breathe in the water The fish breathes by the gills, the gills of the fish are only suitable for absorbing oxygen from the water, and the oxygen in the air cannot be absorbed, and the gills can help the fish absorb the oxygen dissolved in the air, or the shape of the fish is more suitable for life in the water, the main "swimming tool" of the fish is the fin, and the fin is the perfect swimming tool that the fish has evolved into by living in the water for a long time.

Fish can swim in the water because the side structure of the fish is streamlined, which reduces most of the resistance that the fish experiences when swimming, and because the fins are made up of fins and a fin membrane attached to them. Each fin is supported by a row of soft bars or false spines.

Fish generally have caudal fins, dorsal fins, pectoral fins, and pelvic fins, of which the dorsal fin is specially used to master balance, and other mackerel are used to paddle and grasp the direction.

In addition, most of the fish are pointed at the ends and wide in the middle, which can effectively reduce the resistance of the water, and swim quickly and easily.