Distinguish between internal and. external respiration

External respiration is the exchange of O2 and CO2 between the body and the environment. It involves moving air in and out of the lungs and the exchange of gases between the alveoli and the blood capillaries. The gases must also be exchanged between the blood capillaries and the cells of the body. This is called internal respiration

When scientist examine data such as historical documents, they are using the "scientific methods"