If you cover a fire and cut off the air supply, the fire cannot burn. It needs air to burn . in the same way , we need the oxygen which is in air to burn up the food we have eaten and turn it into energy. We get this oxygen through our lungs. We take in aur through our nose and mouth. It passes down our windpipe into our lungs. There,the air passages become smaller until the smallest passage ways end in tiny air sacs called aveoli.
In this aveoli, the oxygen from the air is taken into our bloodstream. At the same time the waste product of the body's processes carbon dioxide is passed back into the aveoli and from there it travels to the lungs to be breathed out as used air. All this takes place in less than a seconds!.
How do fish breathe?
When we breathe , we draw air into our lungs and take from it the oxygen we need in order to remain alive. Like other animals, fish need oxygen in order to live but a fish gets its supply of oxygen not from the air but from the watar in which it swim. It takes watar into its mouth. Then it closes its mouth and squeezes the watar over it gills. There are feathery pieces of tissue on each side of its throat and they are full of tiny blood vessels. Just as our lungs take oxygen out of the air so the gills take oxygen out of the watar. And just as with us, so the waste carbon dioxide is passed back through the gills and the used watar then flows out through the fish's gill slits.
The Respiratory system
Informative article. Exactly the fishes exchange gases through water as they can't live without water. While we, human beings take oxygen from air,