Different animals breathe in different ways. People and all other mammals breathe with lungs. So do all birds and reptiles and most grown-up amphibians. Lungs are made of tiny air sacs joined by little tubes.
All fishes have gills for breathing. Gills are small fringes or sheets of thin "skin." As water flows past them, the gills take in oxygen from the air dissolved in the water. Lungfishes have both gills and lungs. They can breathe either in or out of water.
Some baby insects that live in water have gills just as fishes do. Grownup insects have air tubes. Air travels through the tubes all over the insects' bodies.
Some spiders have air tubes. Others have book lungs. Book lungs are sacs filled with flaps of thin skin like the pages of a book.
Many animals have no special kind of breathing system. The earthworm is one of them. To breathe, it must be in moist soil. Oxygen from the air can then pass into the earthworm's body through its moist skin.
Some animals breathe much faster than others. A tiny pygmy shrew breathes ten times as fast as a person. But breathing, whether it is fast or slow, must not stop. Animals must have oxygen to stay alive.
INTERESTING FACTS ABOUT BREATHING
The air we inhale is approximately 78 percent by volume nitrogen, 21 percent oxygen, 0.96 percent argon and 0.04 percent carbon dioxide, helium, water, and other gases.
Breathing is one of the few bodily functions which, within limits, can be controlled both consciously and unconsciously.
Ancient cultures generally linked the breath to a life force.
It is not possible for a healthy person to voluntarily stop breathing indefinitely.
