Eleanor Lutz, a self-described designer with a molecular biology degree, has created a fascinating animated graphic that demonstrates the means by which three different species, namely humans, birds and grasshoppers, breathe.
Mammals inhale by moving the diaphragm to lower the air pressure in the chest cavity and pull air into the lungs. The human chest cavity is always at a lower pressure than the outside environment (usually 760mmHg at sea level). Birds have air sacs that store and pump air through the stationary lungs. Unlike in mammals, air flows in only one direction through bird lungs. With the help of the air sacs, this allows birds to take in oxygen even during exhalation. … Grasshoppers have no lungs and do not use their circulatory system to move oxygen. They transport air directly to tissue cells using tracheal tubes.
image by Eleanor Lutz