Oxygen cycle is the process due to which the ecosystem maintains its production, utilization and consumption. It is one of the most important biogeochemical cycles. Oxygen is the second most abundant gas in the atmosphere and we are all aware of the significance of oxygen on the sustainable development of living organisms in the ecosystem.
| Table of Content |
Keyterms: Ecosystem, oxygen, biogeochemical cycles, atmosphere, gas, Biosphere, Respiration, Photosynthesis
Check out Natural Resources PYQs: Speed of Rain
Oxygen in Ecosystem
[Click Here for Sample Questions]
Oxygen is unevenly distributed in our ecosystem. It is present in the air we breathe to the water we drink. It is also present in compounds formed with other metals in the atmosphere or inside the earth’s crust. The distribution of oxygen can broadly be divided into:
(i) Oxygen in Atmosphere
The atmosphere is a mixture of gases forming a blanket around the earth. Oxygen constitutes around 21% of the total mixture of gas present in the atmosphere in the form of molecular oxygen. Only 0.35% of total oxygen present on earth is present in the atmosphere.
The liberation of gaseous oxygen in the atmosphere is done by the process known as photolysis. And the process due to which oxygen is returned to the atmosphere is known as photosynthesis.
(ii) Oxygen in Biosphere
An ecosystem where all organisms live is known as a Biosphere. Oxygen present in the biosphere is around 22% in the form of components of organic molecules. An exchange of oxygen takes place between the plant kingdom and animal kingdom in the biosphere through photosynthesis and respiration.
(iii) Oxygen in Lithosphere
The outer part of the earth’s crust is known as the lithosphere. Around 46% of oxygen is present in the lithosphere. These are in the form of oxides, organic content, and mineral deposits. These oxides of metals are formed due to exposure to chemically active elements with oxygen forming respective oxides.
Due to various natural reasons and effects of weather on these compounds, trapped oxygen molecules are released as free oxygen into the atmosphere. Various plants and animals also consume nutrients from the lithosphere and release trapped oxygen into the atmosphere.
(iv) Hydrosphere
The portion of earth covered with water is known as the hydrosphere. It contains around 33% of total oxygen by volume as a component of water. This dissolved oxygen is responsible for the survival of the aquatic ecosystem.
Major processes in Oxygen Cycle
[Click Here for Sample Questions]
The following are the major processes involved in the oxygen cycle.
Photolysis / Photodissociation Process
The process due to which atmospheric moisture and other oxides release free oxygen into the atmosphere by breaking down due to the action of UV radiations on it is called Photolysis.
Photosynthesis Process
The Process in which plants absorb carbon dioxide for the production of glucose and energy, in presence of UV rays while having oxygen liberated into the atmosphere is called photosynthesis.
Photosynthesis Process
Respiration Process
The Process in which humans and animals consume oxygen from the atmosphere for the breakdown of glucose and carbohydrates to release carbon dioxide into the atmosphere, along with the liberation of energy is known as respiration. The cells tissues, muscles and organs require multiple biomolecules like fats carbohydrates, proteins, and fats for their growth and development.
Haemoglobin, a component in the blood of humans, is the carrying medium of oxygen, it carries oxygen to every part of the body as the blood flows through the vessels. This liberated energy during the process of respiration is then used for various metabolic activities by humans and animals.
Organisms that mandatorily require oxygen for their survival and reproduction are termed aerobes. Whereas organisms that do not require oxygen for their growth are termed anaerobes.
Read More:
| Related Articles | ||
|---|---|---|
| Pollination by insects | DNA Genetic Material | Triple Fusion |
Oxygen Cycle
[Click Here for Sample Questions]
The following are the various steps involved in the oxygen cycle.
Conversion of CO2 to O2
During the process of photosynthesis, chlorophyll present in plants uses sunlight along with groundwater and inhales carbon dioxide from the atmosphere and exhales oxygen. It results in the formation of glucose which is utilized by plants to grow and flourish.
Consumption of Oxygen by Aerobes
Human beings, animals, and other aerobes depend on oxygen for multiple biochemical life processes. The availability of oxygen in the atmosphere is very important for their survival and growth.
Glucose and Carbohydrates are formed during the process of photosynthesis when consumed by humans and animals as food. This glucose in food when comes in contact with oxygen during respiration is then converted into carbon dioxide along with the liberation of energy. This energy is then utilized for various metabolic activities.
Conversion of O2 to CO2
As glucose or carbohydrates, in presence of oxygen breaks down into carbon dioxide along with the liberation of energy. The carbon dioxide is released into the atmosphere as a by-product during this process of respiration. This carbon dioxide can later be used in the process of photosynthesis liberating oxygen, this process continues and is termed as oxygen cycle.
Also check:
Things to Remember
- The Oxygen cycle, which is one of the most important biogeochemical processes, explains about formation, consumption, and utilization of atmospheric oxygen.
- Photosynthesis is an essential process for plants for crying out their various metabolic activities, similarly, respiration is also an essential process for sustainable development and various metabolic activities.
- Atmospheric oxygen is liberated in the process of photosynthesis in green plants and oxygen is consumed by aerobes in the process of respiration
- Whereas CO2 is released by aerobes during the process of respiration which is used in the process of photosynthesis.
- This process of O2 production during photosynthesis and utilization during respiration is known as the oxygen cycle.
- Phytoplankton, a plant found in oceans, is responsible for most of the oxygen present in the world, it consumes ammonia and liberates oxygen.
- Photolysis is the process in which UV rays break down oxides and moisture in the atmosphere to release oxygen into the atmosphere.
Sample Questions
Ques. What are the two forms of oxygen found in the atmosphere? (2 marks)
Ans.
- Elemental oxygen is normally found in the form of a diatomic molecule (O2) in the lower regions of the atmosphere to the extent of 21%. It is a non-poisonous form of oxygen.
- But in the upper reaches of the atmosphere (stratosphere), it occurs in the form of ozone, containing three atoms of oxygen and having the molecular formula O3. It is the poisonous form of oxygen
Ques. What are the three ways by which CO2 is returned back into the atmosphere? (2 marks)
Ans. The three ways by which CO2 is returned back into the atmosphere are :
- By the decomposition of dead organic matter.
- As the product of respiration by both plants and animals.
- As the gaseous waste formed by the combustion of fuels like coal, wood, petrol and gaseous fuels.
Ques. Define biosphere. Name its components. (2 marks)
Ans. The life-supporting zone of the Earth where the atmosphere, the hydrosphere and the lithosphere interact and make life possible is known as the biosphere.
Two components of the biosphere ate :
(i) Biotic: All living forms such as plants, animals and microorganisms.
(ii) Abiotic: Air, water and the soil.
Ques. List any three human activities which would lead to an increase in the carbon dioxide content of the air. (3 marks)
Ans. Three human activities which would lead to an increase in the CO2 content of air are :
- Respiration: It is the natural process of release of CO2 by both plants and animals. But this release is neither dangerous nor has any adverse effect on our environment.
- Combustion of fuels: The various types of fuels are burnt to provide energy for various –needs like heating, cooking, transportation and industrial fuels.
- Deforestation: Trees help in the conversion of CO2 into organic compounds such as glucose, starch etc., by the process of photosynthesis. When these trees are cut non- judiciously, then the level of CO2 increases in our environment.
Ques. Draw labelled diagram of Oxygen cycle. (2 marks)
Ans. Oxygen from the atmosphere is used up in combustion, respiration and
in the formation of oxides of nitrogen. Oxygen is returned to the atmosphere through photosynthesis. This constitutes the oxygen cycle in nature.
Ques. Why is the atmosphere essential for life? (5 marks)
Ans. The atmosphere is essential for life because of the following reasons :
(i) It keeps the average temperature of the earth fairly steady during the day and even during the whole year.
(ii) It prevents the sudden increase in temperature during the daylight hours.
(iii) It contains all the important gases which are required for sustaining life on earth. These gases are :
- Oxygen for respiration of living organisms and oxidation.
- Carbon dioxide for photosynthesis in plants and for making food.
- Nitrogen for providing an inert atmosphere and making proteins.
(iv) The stratosphere region (16-23 km from the surface of Earth) of the atmosphere contains a thick layer of ozone which filters the harmful UV radiation from the Sun. If these radiations reach the surface of Earth, then they may cause cancer in animals and are also harmful to plants.
Ques. State two ways in which atmospheric carbon dioxide is fixed. (2 marks)
Ans.
- Carbon dioxide is fixed into carbohydrates by the process of photosynthesis.
- The carbon dioxide is fixed in the form of carbonates and bicarbonates; compounds and endoskeletons and exoskeletons of various animals are formed from carbonate salts.
Ques. Carbon dioxide is necessary for plants, justify this statement. Why do we consider it a pollutant? (2 marks)
Ans. Carbon dioxide is indeed necessary for plants as it is used in photosynthesis. In photosynthesis, carbon dioxide is fixed into carbohydrates. Excess quantity of carbon dioxide results in the greenhouse effect and leads to global warming. The excess carbon dioxide in the air may cause several respiratory problems in living beings. Therefore, carbon dioxide, if produced in excess quantities, is considered a pollutant.
Ques. What is the importance of the carbon cycle? (2 marks)
Ans. It helps to maintain a constant level of CO2 in the earth’s atmosphere which further helps in maintaining the earth’s temperature through the greenhouse effect.
Ques. Give two examples where oxygen is not playing any role in supporting life. (2 marks)
Ans.
- Some bacteria are poisoned by elemental oxygen.
- The process of nitrogen-fixing by bacteria does not take place in the presence of oxygen.
Read More:
Comments