how do living things breathe?
Answers
WHY DO I BREATHE?
Take a deep breath of air. How long can you hold it? Thirty seconds? One minute? Then you must
breathe again. Most of the time you breathe without even thinking about it. Have you ever wondered:
Why do I breathe?
THE AIR YOU BREATHE
Air is all around you. You can not see it, but you can feel it when it moves. If you hold your hand
close to your nose and mouth, you can feel the warm air every time you exhale.
Air is a mixture of invisible gases. Most of it (almost four-fifths) is nitrogen. About one-fifth of the air
is oxygen. There are also small amounts of other gases, like carbon dioxide and water vapor, plus
dust, dirt, pollen and pollution.
Like everything else around you, gases are made of very tiny particles called molecules. These
molecules are always moving. They continually bump into each other and nearby objects. The push, or
force, from the moving air molecules is called air pressure.