Answer:
As they produce food by the process of photosynthesis which cannot be done by anyone else. Plants use chlorophyll, CO2 and H2O in photosynthesis( which is a biochemical process). Plants became a cause of life on earth. Hence plants are the ultimate source of food on earth.
Answer:
The Cardiovascular System
Explanation:
The respiratory system draws air into the lungs. Oxygen diffuses through the walls of the alveoli and across the walls of the capillaries where it enteres the bloodstream. The oxygen molecules are picked up by red blood cells, which are pumped through the blood vessels by the action of the heart. As the red blood cells carrying oxygen pass through capillaries near the cells, oxygen diffuses into the cells.
