how does an organism obtain oxygen for aerobic respiration

From the air we breathe

Explanation:

Oxgyen is breathed into the lungs and transported round the body through blood, this oxygen is transport to the mitochondria of every cell where respiration is carried out

youre right there are

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.