The exchange of gases between the environment and the respiratory organs of vertebrates is referred to as

Step 1: Analyze the question The question asks for the term that describes the exchange of gases between the environment and the respiratory organs (e.g. lungs) of vertebrates. Note that it is about the movement of air in and out of the body, not about what happens inside the cells.

Step 2: Explain the concepts

• Inhalation (inspiration): only the taking in of air. It is just one half of the process.
• Expiration (exhalation): only the giving out of air. It is the other half.
• Breathing (ventilation): the physical process of taking air in and giving it out, which exchanges gases between the environment and the lungs or other respiratory organs.
• Respiration: the chemical process in the cells in which food (glucose) is oxidised to release energy, carbon dioxide and water. It takes place inside the cells, not between the environment and the lungs.

Step 3: Work through the options

• A. Inhalation covers only air going in, so it is incomplete.
• B. Respiration is a cellular chemical process, so it is wrong here.
• C. Expiration covers only air going out, so it is incomplete.
• D. Breathing covers both air going in and air going out between the environment and the respiratory organs. This fits.

Step 4: Answer The correct answer is D. breathing.

Exam tip: Remember "Breathing = Bellows (lungs pumping air); Respiration = Release of energy in cells." If a question mentions the environment and the lungs, think breathing. If it mentions cells, energy, or mitochondria, think respiration.