<span>respond to their environment
grow and change
reproduce and have offspring
have a complex chemistry
maintain homeostasis
are built of structures called cells
<span>pass their traits onto their offspring</span></span>
The digestive system works very closely with the circulatory system to get the absorbed nutrients distributed through your body.
It is a perfect example of a natural selection.
(I'm not sure if this is the exact answer that you are looking for.)
The location that should have lowest oxygen concentration would be the tissue because it is the furthermost location.
Other location with lowest oxygen concentration should be in the right part of the heart. It is when all unoxygenated blood pooled before going to the lungs. But the left part of the heart will have highest oxygenated blood, so it's ambiguous.
High oxygen concentration should be found in the environment, lungs, and the blood.
