According to the theory of mitochondria in cells today are the descendants of aerobic prokaryotes that used oxygen to generate energy.

Endosymbiotic

Explanation:

Remember that the endosymbiotic theory says that the mitochondria was once a free prokaryotic cell that was engulfed by a larger cell this is why the mitochondria has its own DNA and it also has its own process of division separate from the cell itself.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.