Plants and animals die without air. Why? Which gases do plants and animals inhale and exhale? What are the role of these gases in plants and animals? (Note: Air is composed of 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and other minor gases).

Plants and animals both are living organisms that are directly dependent on the air. The air is comprised of various gases with definite proportions such as  78% of nitrogen, 21% of O₂, 0.9% of argon, 0.03% of CO₂, and other minor gases.

Oxygen (O₂) is the main gas that is essential for life to exist. Without this gas, no organisms can survive.

The organisms inhale oxygen (O₂) gas and exhale carbon dioxide (CO₂) gas.

These gases play an important role in the lives of plants and animals as it helps in carrying out the process of respiration. This process is essential in order to generate energy in the body of the organisms where the food particles (commonly known as sugar) are disintegrated by the cells. This is how an organism respire by inhaling O₂ gas and exhaling CO₂ gas.

the correct answer is:

a population changes in response to a change in the environment.

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