Dogs, people and fish breathe the same reason. Everyone needs oxygen. Oxygen is gas that the bodies are used to produce energy.
Living creatures experience two feelings of hunger gastric and oxygen. Unlike interruptions between meals, breaks between breaths are much shorter. People make about 12 breaths per minute.
It may seem that they breathe only with oxygen, but there are many other gases in the air. When we inhale, the lungs are filled with these gases. The lungs separate oxygen from the air and release the remaining gases that the bodies do not use.
All exhale carbon dioxide, which the bodies produce when it produces energy. Just as the body swears when you play sports, the body also releases carbon dioxide when we breathe.
Pisces also need oxygen to move the body, but the oxygen that they use is already in water. Their bodies are not like people. People and dogs have lungs, fish have gills.
How the gills work
Fish gills are visible when they look at their heads. These are lines on the sides of the head of fish. Gills are also inside the body of fish, but they cannot be seen outside just like our own lungs. You can see how the fish breathes in water, because her head becomes more when she picks up water. Just like when a person swallows a large piece of food.
First, water enters the mouth of fish and flows through the gills. When the water leaves the gills, it returns to the reservoir. In addition, carbon dioxide, which produces the fish, also removes with water when it leaves gills.
Funny fact: fish and other animals with gills breathe oxygen, because their blood flows through gills in the opposite direction from water. If blood flowed through the gills in the same direction as the water, the fish would not have received the necessary oxygen from it.
Gills are like a filter, and they collect oxygen necessary for breathing from the water. After the gills absorb oxygen (oxygen cycle), gas spreads through the blood and nourishes the body.
This is why it is so important to leave fish in water. Without water, they will not receive the oxygen necessary for health.
Other respiration mechanisms in fish
Many fish breathe through the skin, especially when they are born, because they are so small that they do not have specialized organs. With rush, gills develop, because diffusion through the skin is not enough. 20% or more skin gas exchange is observed in some adult fish.
Some species of fish have developed cavities behind the gills that are filled with air. Others have complex organs developed from irrigated gill arcs form and act as a light.
Some fish breathe air without special adaptation. American eel covers 60% of the needs of oxygen through the skin and 40% swallows from the atmosphere.
