Replacement of Oxygen in the Atmosphere: Have you ever heard of photosynthesis? Yes, it is the process of converting water, sunlight, and carbon dioxide into oxygen and simple sugars that the plant uses as fuel. Photosynthesis helps to balance the oxygen in the Atmosphere by using the carbon dioxide released into the Atmosphere by the process of respiration by human beings, animals and by burning fuel. In this article, we will learn more about how the replacement of oxygen in the atmosphere takes place.

Define Atmosphere

The envelope of air that surrounds the Earth is called the Atmosphere. The Atmosphere extends up to many kilometers above the Earth’s surface. We live in the Atmosphere of the Earth. The Atmosphere is essential for life on Earth. This is because the air in the Atmosphere provides oxygen to all living organisms, including us, for us to breathe. The higher we are in the Atmosphere, the less is the amount of air. The air on very high mountain tops is so thin that people do not have enough oxygen to breathe properly. So, people who climb high mountains (called mountaineers) carry oxygen gas cylinders with them. They breathe oxygen from these cylinders to survive in the high mountains.

The Atmosphere is divided into a series of concentric shells or spheres due to variations in temperature and pressure at various altitudes. There are four atmospheric layers: troposphere, mesosphere, and thermosphere.

Troposphere: It is the lower part of the Atmosphere. We, humans, live in the troposphere, and almost all the weather happens in this bottom layer. It extends to about \(8 – 16{\text{ km}}\) of altitude from the Earth’s surface. It contains more than \(90\) percent of the gases in the Atmosphere. The transition zone between the troposphere and the stratosphere is known as tropopause. The average of the troposphere is \({15^{\text{o}}}\,{\text{C}}\) near the ground surface. In the tropopause, it descends to \(- {57^{\text{o}}}{\text{ C}}\).

Stratosphere: It extends up to \(30 – 50{\text{ km}}\). There are few mixing of gases in the troposphere and stratosphere. It is also known as the ozone layer because there is a thin ozone layer in the stratosphere at an altitude of
\(15 – 30{\text{ km}}\). The transition layer between the stratosphere and the mesosphere is called the stratopause. The ozone shield absorbs harmful VU radiation from the sun.

 Mesosphere: extends up to a height of \(80{\text{ km}}\) above the stratosphere. Shows a decrease in temperature with altitude. The top of this layer is the coldest place in the Earth’s system, with an average temperature of around minus \(85\) degrees Celsius.

Thermosphere: a layer of air that extends up to \(100{\text{ km}}\) beyond the mesosphere. It shows an increase in temperature with height.  Particles are ionized as a result of the high temperature. As a result, it is also referred to as the ionosphere. Because it contains the warmest temperatures in the Atmosphere, the thermosphere is often referred to as the “hot layer.” The temperature rises with altitude until it reaches the estimated top of the thermosphere at
\(500{\text{ km}}\).

Composition of Air

Now we will describe what air is made of. This is known as the composition of the air. We know that air is a gas. For a long time, it was thought that air was just a gas. Now it has been shown by experiments that air is not a single gas. Air is a mixture of many gases. The main component of air is nitrogen gas. Almost four-fifths of the air is made up of nitrogen. The second main component of air is oxygen gas. About a fifth of the air is made up of gaseous oxygen. Besides nitrogen and oxygen gases, air also contains small amounts of carbon dioxide gas, water vapor, and some other gases like argon and helium, etc. The air can also contain some dust particles. We can now describe the composition of air as follows and the air is primarily a mixture of nitrogen and oxygen gases with small amounts of carbon dioxide, water vapor, and other gases. Some dust particles can also be present in the air. The composition of air as a percentage of its various components can be written as follows:

Composition of Air

Gases	\(\%\) proportion
Nitrogen	\(78\% \)
Oxygen	\(21\% \)
Carbon dioxide	\(0.03\% {\text{ }} – {\text{ }}0.04\% \)
Inert gases	\(0.9\% \)
Water vapour	Variable
Dust particles	Variable
Impurities	Variable

How is Oxygen in the Atmosphere Replaced?

The oxygen in the air is constantly used by living creatures for breathing. Oxygen is also used to burn fuels. So how is oxygen in the air exchanged? 
Oxygen consumed by animals and humans when breathing and burning fuel is continuously replaced by plants during photosynthesis.

Photo means light, and synthesis means putting together.

“Photosynthesis is the process by which green plants prepare their own food in the presence of sunlight using carbon dioxide and water.” Food is prepared in the form of carbohydrates with the release of gaseous oxygen.

Plants take carbon dioxide from the air and water from the soil for photosynthesis. This process only occurs in green plants because they contain a green pigment called chlorophyll that is able to capture the sun’s energy from the sun. Therefore, it only happens during the day, while breathing occurs both during the day and at night. Although glucose is produced during photosynthesis, it is stored in plants as starch.

During the respiration of plants and animals, food is broken down with the help of atmospheric oxygen to form carbon dioxide, water, and energy. While the photosynthesis of green plants removes carbon dioxide from the air, the respiration of living things returns carbon dioxide to the air. So these two opposing processes together keep the air composition constant. The oxygen produced during photosynthesis mixes with the air and makes it fresher, i.e., maintains the required amount of oxygen in the air. Plants also keep the required amount of carbon dioxide in the air, using it constantly.

Why does Oxygen in the Atmosphere not get Finished?

All humans, plants, and animals use atmospheric oxygen for respiration. However, the percentage of oxygen in the Atmosphere remains constant for many years and does not decrease because green plants are able to photosynthesize by absorbing \({\text{C}}{{\text{O}}_2}\) from the Atmosphere and conversely produce \({{\text{O}}_2}\). It is this process that has kept the oxygen levels quite stable.

Summary

The envelope of air that surrounds the Earth is called the Atmosphere. The Atmosphere is divided into a series of concentric shells or spheres due to variations in temperature and pressure at various altitudes. There are four atmospheric layers: troposphere, mesosphere, and thermosphere. Air is a mixture of many gases. The main component of air is nitrogen gas. The second main component of air is oxygen gas. Air also contains small amounts of carbon dioxide gas, water vapor, and some other gases like argon and helium, etc. Oxygen consumed by animals and humans when breathing and burning fuel is continuously replaced by plants during photosynthesis. “Photosynthesis is the process by which green plants prepare their own food in the presence of sunlight using carbon dioxide and water.”

FAQs On Replacement of Oxygen in the Atmosphere

Q.1. Name the process that replaces oxygen in the Atmosphere.
Ans: The process which replaces oxygen in the Atmosphere is photosynthesis.

Q.2. How does oxygen get added to the Atmosphere?
Ans: Oxygen gets added to the Atmosphere by the process of photosynthesis. “Photosynthesis is the process by which green plants prepare their own food in the presence of sunlight using carbon dioxide and water.” Food is prepared in the form of carbohydrates with the release of gaseous oxygen.

Q.3. Who plays the main role in the replacement of oxygen in the Atmosphere?
Ans: Green plants play the main role in the replacement of oxygen in the Atmosphere.

Q.4. What percentage of oxygen is in the Atmosphere?
Ans: The percentage of oxygen in the Atmosphere is \(21\% \)

Q.5. What is the hottest layer of the Atmosphere?
Ans:  The hottest layer of the Atmosphere is the thermosphere.

Q.6. What is the coldest layer of the Atmosphere?
Ans: The coldest layer of the Atmosphere is the mesosphere.

Study Physical Nature Of Matter

We hope this detailed article on the Replacement of Oxygen in the Atmosphere has helped you. If you have any queries, drop a comment below, and we will get back to you.