Answer:
External respiration:
External respiration may be defined as the process of exchange of carbon dioxide and oxygen between the body and external environment. This is a mechanical process and may or may not require ATP. Only gases are exchanged in the external respiration process. This process may be voluntary or involuntary in nature.
Internal respiration:
Internal respiration may be defined as the process of diffusion of oxygen from blood into the interstitial fluid and carbon from the interstitial fluid into the blood. This is a chemical process that requires ATP. Nutrients are broken down into smaller substances and ATP is produced during this process. Internal respiration is an involuntary process.