Oxygen is one of the most important molecules needed for growth and to sustain life. Humans and other mammals take in oxygen through respiration. We breathe and inhale oxygen into our lungs, which then disperses oxygen to all tissues via blood blood flow. Other creatures in our world clearly do not have lungs, so they cannot use this method for dispersing oxygen through their bodies. In particular, the way insects breathe is interesting to study.

Insects breathe or gather oxygen through a branched network of tubes called tracheae. These tubes have openings, called spiracles, located on the thorax (chest) and abdomen. Oxygen passively enters spiracles, flows down the tubes, and ends up in liquid located at the bottom of each tube that helps the oxygen dissolve. This liquid then moves into other cells, to provide oxygen to other cells in the insect body.

You can see, under microscope, insects breathe or take in air through their mouths, but they seldom yawn. And this air through the mouth doesn’t provide needed oxygen to the cells because insects lack lungs. Instead of using air in the mouth to supply lungs with oxygen, it can be said that insects breathe passively. They must rely on oxygen around them entering their spiracles, making way down their tracheae to provide needed oxygenation of all their cells.