1. They need oxygen to survive. This is because oxygen allows them to extract energy to use.

2. It gets to the cells from the lungs. For the oxygen to get to the lungs, people need to inhale it and it needs go down the trachea. Then, the lungs transfer the oxygen to the red blood cells in the blood stream. The cell picks up the oxygen from the red blood cells.

3. The lung tissues, epithelial tissue, and red blood tissues.

4. The lungs, the heart, the trachea, and the blood vessels.

5. The respiratory and circulatory systems.