This is produced when the body uses oxygen to produce energy. CO2 is transported by the blood to the lungs where it is exhaled.
2. Urea:
This is produced when proteins are broken down. Urea is transported by the blood to the kidneys where it is filtered out and excreted in the urine.
3. Feces: This consists of undigested food material and bacteria. Feces are produced in the intestines and expelled through the rectum.