As the surface grew 4.6 billion years ago, oxygen was not present in the atmosphere. As life started evolving on the planet 3.6 billion years ago, cyanobacteria and primitive life forms started synthesizing oxygen. The oxygen was gradually produced over a carboniferous period of 299 million years and it developed to the extent that we know of now.
Almost 21% of the earth's atmosphere comprises oxygen. It is the second most abundant gas available in nature after nitrogen. Human beings respire oxygen and utilize oxygen for their metabolic activities. The cells, tissues, and organs require oxygen for their growth and development. In human beings, oxygen is carried by hemoglobin present in the blood to various organs in the body. It is also crucial in the formation of multiple biomolecules like carbohydrates, fats, proteins, and vitamins.
What is the Oxygen Cycle?
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The oxygen cycle is one of the most important biogeochemical cycles present in nature and comprises production and consumption or utilization of oxygen in the environment. It is a biological process in which the oxygen travels through the lithosphere, biosphere, and atmosphere. The earth's crust comprises land and water, which is the lithosphere. It is the outer part of the earth's crust and is the largest oxygen reservoir. The biosphere is the living ecosystem present on the planet where an organism lives. The atmosphere is the blanket of air present around the earth consisting of a mixture of gases like oxygen, nitrogen, and other gases. The oxygen cycle is the flow of oxygen molecules through these spheres. The flow of nitrogen, oxygen, carbon, and water cycles in nature is essential for the sustainable development of the living components of the ecosystem.
Stages of the Oxygen Cycle
There are three stages involved in the oxygen cycle. They are:
Step 1: All green plants produce food through the process of photosynthesis. During photosynthesis, the green plants use carbon dioxide, sunlight, chlorophyll, water to form glucose. Oxygen forms as a by-product by plants in this process. This oxygen released into the atmosphere. Oxygen forms appropriating photodissociation. Photodissociation is the dissociation of water vapor molecules in the atmosphere, which form oxygen as a by-product. Thus, releasing the oxygen into the atmosphere.
Stage 2: It consists of the consumption and utilization of oxygen by aerobic organisms. The oxygen is used for the various biochemical processes in the body. Several life processes depend on the availability and consumption of oxygen. Animals respire the oxygen produced in nature, which in turn helps in their growth and development.
Stage 3: The aerobic organisms which have used the oxygen, now release carbon dioxide into the atmosphere. The process of respiration is the inhalation of oxygen and exhalation of carbon dioxide. The food consumed by the aerobes is digested with the help of oxygen to form water, carbon dioxide, and energy in the form of calories. Aerobes require energy for any activity performed by their bodies. Hence, the formed carbon dioxide is released back into the atmosphere through respiration, and carbon dioxide reaches back. The plants use the same carbon dioxide, and the cycle continues. This cycle restores the oxygen content in the biosphere, and the period is crucial for life to grow and survive.
Uses of Oxygen
Oxygen has many functions in nature. Few of them include:
Breathing: Humans and other organisms utilize oxygen for metabolism and digesting food. This process helps in the differentiation of cells, breaking down glucose in Glycolysis, Kreb's cycle, and means that it helps in absorption and formation of biomolecules in the organisms. Carbon dioxide is a product of these processes in the body which is exhaled by the aerobes.
Decomposition: It is one of the natural processes that occur in nature. The fungi, bacteria, insects further decompose the dead and decayed organic matter in the soil, and saprophytes present in the ground. During the process, they utilize atmospheric oxygen and release carbon dioxide.
Combustion: It is a process where heat is released by burning organic matter, wood, fossil fuel in the presence of atmospheric oxygen. Oxygen is an essential element required for combustion. It releases carbon dioxide into the atmosphere.
Rusting: The oxidation of metals and alloys with prolonged exposure to atmospheric oxygen and moisture is called rusting — oxides of iron forms around iron when the iron is in humid conditions for an extended period. New compounds form on the surface of the metal during rusting.
Production of Oxygen
There are two ways in which oxygen is formed in nature. They are:
Photosynthesis: It is a complex process used by green plants where the leaves of the green plants with the help of sunlight and chlorophyll convert carbon dioxide and water into glucose and oxygen. The glucose produced is transferred to the fruits and edible parts of the plant. As already explained, the oxygen released into the atmosphere as a by-product of this process.
Photodissociation: It is the formation of oxygen molecules when sunlight interacts with the water vapor present in the atmosphere. Water vapor exists in the atmosphere as a result of the water cycle. The destruction of the ozone layer by various gases can also lead to the formation of molecular oxygen.
Some Interesting Facts on Oxygen
Phytoplanktons are plants existing in the marine ecosystem, which can consume ammonia. These are the primary plants that release most of the oxygen present in the world. Almost 80% of the oxygen currently present in the world is due to the action of phytoplankton.
The earth's crust also has a reservoir of oxygen, but it cannot be used for respiration as all the oxygen is present in the form of oxides.
Sunlight and water vapor can react with each other to form oxygen, and this process is called photodissociation.
If a person does not receive oxygen to any organ of the body for a prolonged time, cells of the organ get damaged permanently and cannot be regenerated.
Trees produce oxygen only in the day time with the availability of sunlight. At night trees also produce carbon dioxide and carry on respiration.
Oxygen can be stored in cylinders, and for people with respiratory distress and problems with respiration, oxygen is given directly to maintain the oxygen saturation of the body.
Importance of the Oxygen Cycle
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The oxygen cycle is an essential biogeochemical cycle to maintain the concentration and level of oxygen in the atmosphere. The oxygen cycle is one of the main reasons for the existence of life on earth. Without oxygen, the biosphere could not exist. However, Anaerobes can live without the presence of oxygen. Few anaerobes called the obligate anaerobes might even die due to the presence of oxygen.
The critical functions of oxygen include breathing, combustion, rusting, and decomposition.
Oxygen Cycle Overview
The oxygen is first produced by plants by the process of photosynthesis. This oxygen is circulated in the atmosphere, which is inhaled by organisms that require oxygen for living. The microorganisms and other animals utilize oxygen and utilize it for their metabolism. They release carbon dioxide as a by-product into the atmosphere and which is again used by plants.