Recycling

Key Concepts

• Ecosystem
• Carbon cycle
• Nitrogen cycle
• Oxygen cycle
• Phosphorous cycle
• Sulfur cycle

Introduction: 

When a tree is dead it breaks down into simple substances and gets mixed in the soil with the help of microorganisms that as fungi and bacteria, and this is called decomposition.  

This is an example of how matter like carbon present in the tree reaches the soil and later gets transferred to living and non-living materials.  

 Matter needs to get transferred from living and non-living materials by nutrient recycling. 

Explanation: 

Carbon Cycle

Carbon is the most important constituent of all living cells. 

It also forms the major portion of oceans, rocks, and sediments of the earth. Through these reservoirs, the carbon gets recycled from the atmosphere to the environment and again back to the atmosphere. 

Humans contribute majorly to the cycle by burning fossil fuels. 

The Carbon Cycle is important as the main element ‘Carbon’ that sustains life is transferred from living organisms to the atmosphere and environment. 

Even after the death of organisms, carbon is still reserved as fossil fuel in the soil. So, there is a balance of carbon maintained. 

The following picture further explains the amount of carbon present on the land, water, and atmosphere in Gigatons (GT). 

Nitrogen Cycle  

Nitrogen is the main element of amino acids, and DNA and hence its presence in all living forms. It is very important for plants as it is the main component of chlorophyll. The form in which it is present in the atmosphere makes it unavailable to plants. So, it is made available through biological and chemical cycles. 

Let us understand the Nitrogen Cycle. 

As Nitrogen is not directly taken by the plants it is converted to the following for the plant uptake. 

1. Fixing atmospheric nitrogen to ammonia by certain bacteria in the roots of leguminous plants is called Nitrogen Fixation. 
2. The ammonia is then converted to nitrite by Nitrosomonas bacteria and then to nitrate by Nitrobacter species, this entire process is called Nitrification. 

2NH₄⁺ + 3O₂ → 2NO₂^– + 4H⁺ + 2H₂O 

Ammonia to Nitrite 

2NO₂^– + O₂ → 2NO₃^– 

Nitrite to Nitrate 

3. The dead and decay in the soil are further decomposed by bacteria and fungi that contain nitrogen in amino acids and DNA in organic form is converted to inorganic nitrogen as ammonia, this process is called Ammonification. 
4. Later the nitrates and other nitrogen compounds are taken up by the roots in the soil, this method is called Assimilation. In plants, they serve as the main components of Biomolecules. 
5. Then the nitrogen present in the nitrate form is converted back to gaseous Nitrogen and released into the atmosphere by denitrifying bacteria and the method is called Denitrification.  

Oxygen Cycle

Oxygen is a vital element present in the atmosphere, it is required for respiration, for combustion. 

It is a component of water. 

It is required in the decomposition of organic matter. 

It is present in water as a dissolved form and supports life. 

The atmospheric air consists of different gases like Nitrogen (71%), Oxygen (21%), Argon, and other trace gases (1%). 

Though oxygen is next abundant to nitrogen in the atmosphere, it is important to maintain the cycle of oxygen as it is essential for all living organisms. Also, it forms an essential component in biomolecules and proteins. 

Phosphorous Cycle

Phosphorus is present in every living organism, it is important in the formation of DNA, RNA, and ATP. A certain amount of phosphorous present in rock is washed into the soil by weathering and erosion processes. 

Phosphorous is present in the environment and land. Hence, the atmosphere has no role to play in the phosphorous cycle. 

The Sulfur Cycle

Rocks and Mountains are reservoirs of Sulphur. It is released by weathering activities in the soil. 

Sulfur is required by all plants and living organisms as it is present in proteins. In the amino acids like cysteine and methionine. 

Sulfur in the atmosphere is released by burning fuels, volcanic activities, and the decomposition of organic matter.

Summary

• In an ecosystem, every organism depends on the other organism for food, and shelter and also depends on non-living materials like air, water, minerals, etc.
• Matter needs to get transferred from living and non-living materials by Nutrient Recycling.
• Carbon is the key constituent of all living cells.
• It also forms the major portion of oceans, rocks, and sediments of the earth.
• The carbon cycle is important as the main element ‘Carbon’ that sustains life is transferred from living organisms to the atmosphere and environment.
• Nitrogen is the main element of amino acids, and DNA, and hence its presence in all living forms.
• It is very important for plants as it is the main component of chlorophyll.
• Fixing atmospheric nitrogen to ammonia by certain bacteria in leguminous plants is called Nitrogen Fixation.
• The ammonia is then converted to nitrite by Nitrosomonas bacteria and then to nitrate by Nitrobacter species, this entire process is called Nitrification.
• The dead and decay in the soil is further decomposed by bacteria and fungi that contain nitrogen in amino acids and DNA in organic form is converted to inorganic nitrogen as ammonia, this process is called Ammonification
• Later the nitrates and other nitrogen compounds are taken up by the roots in the soil, this method is called Assimilation.
• Then the nitrogen present in the nitrate form is converted back to gaseous Nitrogen and released into the atmosphere by denitrifying bacteria and the method is called Denitrification.
• The atmospheric air consists of different gases like Nitrogen (71%), Oxygen (21%), Argon, and other trace gases (1%).
• Phosphorus is present in every living organism, it is important in the formation of DNA, RNA, and ATP.
• Rocks and mountains are the reservoirs of Sulphur, it is released by weathering activities in the soil.
• Sulfur is required by all plants and living organisms as it is present in proteins. In the amino acids like cysteine and methionine.
• Sulfur in the atmosphere is released by burning fuels, volcanic activities, and the decomposition of organic matter.