Why do the fish we eat live in the water?

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.

Heart-atrium-ventricle, a circulatory route, arterial blood and venous blood are mixed, which is mainly determined by the fish's own respiratory organs and breathing patterns, that is, the principle of survival of the fittest. It's the same as one can't live in water. What kind of environment makes what kind of creatures.

This 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, more oxygen is obtained by increasing the amount of oxygen that takes in the dissolved oxygen in the water. 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.

Fish belong to the lower animals of vertebrates, and the gills of fish are only adapted to absorb oxygen from the water, but not to the oxygen in the air, so the fish can only live in the water. Fish have gills that help fish absorb oxygen dissolved in the air. The main "swimming tool" of fish is the fin, which is the perfect swimming tool that fish have evolved into after living in the water for a long time.

Characteristics of life

Most of the fish are pointed at the end and wide in the middle, which can effectively reduce the resistance of the water. Fish live in water because they breathe with their gills, and fish are unable to take in oxygen in the air after they leave the water. Since they have no limbs and cannot adapt to life on land, they are more convenient to swim and hunt in the water.

However, there are also some fish that can live out of the water for a short time, such as climbing perch, which can be inhaled in the air with a gill appliar.

Mudskippers can breathe, while African lungfish can lie dormant in the mud for months. The color of the body of the fish is dark at the top and light at the bottom, which 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.