Carbon oxygen , nitrogen and water are essential nutrients for life.In natural ecosystems, these natural ecosystems , these nutrients are released back into soil when organisms die.Decomposers , for example , fungi , and bacteria, break  down dead organisms.The materials locked up in the dead organisms can then be returned to the physical environment to be used again by green plants.Hence, in a balanced ecosystems , nutrients are never lost but are continually recycled.The cycling of these nutrients is brought about by physical , chemical and biological processes, involving both the abiotic and biotic environments.
Nutrient Cycling in an Ecosystems

Nutrient cycles are delicately balanced in nature.Human activities have been upsetting  these cycles, causing many ecological problems.

Robbing nutrient cycles

What happens when you harvest some vegetables or some fruits ?

The nutrients that the vegetables or fruits contain have been removed from the environment in which they grew.These nutrients go into your body.Unless your urine or faeces and your body are allowed to decompose where the vegetables were grown , the soil will lose nutrient.Farmers replace these nutrients by adding fertilisers to the soil.

The carbon cycle

Carbon is constantly being removed from and released into the environment , in the form of carbon dioxide.Hence, the carbon dioxide concentration in the environment remains relatively constant.The various processes by which carbon, in the form of carbon dioxide , is removed from and released into the environment make up the carbon cycle.

Removal of carbon dioxide from the environment

During photosynthesis , green plants absorb carbon dioxide from the atmosphere and use it to manfacture  carbohydrates, for example , glucose.↓

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1. Glucose may be changed to other organic compounds such as fats, amino acids and proteins.

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1. When animals feed on green plants, the carbon compounds become part of the bodies of these animals.

2. The carbon compounds may also be preserved in fossil fuels such as coal , natural gas and oil.

              Release of carbon dioxide into the environment

       Carbon dioxide  is released into the environment through

1. Respiration

When living organisms respire, carbon compounds  like glucose are broken down in their bodies and carbon dioxide is released into the environment.
Nutrient Cycling in an Ecosystems

2. Combustion

When fossils fuels like coal and natural gas are burnt or undergo combustion, carbon compounds presented in the fossil fuels are broken down and carbon dioxide is released into the environment.

3. Decay

When organisms die, their bodies decay or are broken down into simple substance by decomposers.Carbon dioxide is one of the simple substances released into the environment during decay.Also , some of the simple substances are absorbed by decomposers and become part of their bodies.When the decomposers respire, carbon dioxide is released into the environment.An example of such a decomposer is Methanobacterium, which utilises acetate and produces methane and carbon dioxide.
Nutrient Cycling in an Ecosystems

Importance of carbon cycle

The carbon cycle ;

Ensures that there is a continuous supply of carbon dioxide for plants to carry out photosynthesis.Photosynthesis converts energy from the sun into chemical energy in food, which other non-photosynthetic organisms can use to stay alive.

Enables energy to flow through the ecosystem.Carbon compounds carry the trapped solar energy from organisms to organisms in the food chains of an ecosystems.

The greenhouse effect
The burning of organic compunds releases carbon dioxide into the air.With industrialisation and increasing car populations,  more and more carbon dioxide is being released into the atomicsphere.Carbon dioxide forms a layer over the earth's surface  which alows heat  from the sun to enter bur not to escape.Hence , heat is trapped within this layer of gas around the earth.This is called the greenhouse effect.The greenhouse effect might lead to global warming.The world temperature may rise.Icebergsmay melt, releasing a lot of water into the oceans.The sea level may rise and many low-lying countries may be flooded or submerged.
Nutrient Cycling in an Ecosystems
Nutrient Cycling in an Ecosystems by Eachknowledge.blogspot.com