The Carbon Cycle

Nutrient cycles 

Elements pass between the living world and the non-living world- air, water, soil, and rocks. In a constant cycle. 

As living things gow- they take in elements- including, carbon and nitrogen- to use in thier bodies.

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Carbon in Living and Non- living world 

Carbon- one of the most common elements in living things. All of our majour molecules, including carbohydrates, proteins, fats and DNA, contain carbon. 

The process of carbon moving between the living and non-living world is called THE CARBON CYCLE. 

Carbon in present in the atmosphere as carbon dioxide. 

Carbon dioxide is absorbed by plants and buit into carbohydrate molecules such as sugars- this happens during photsynthesis.

The plant uses some of the sugars to make other molecules such as cellulose, fats and proteins, which it uses to grow. 

Plants are eaten by animals and so these carbon compounds can pass into animals and become part of thier bodies. 

Both plants and animals respire- This returns some of the carbon dioxide back into the atmosphere. 

When plants and animals die, soil bacteria and fungi known as decomposters digest thier bodies in the process fo decay and carbon dioxide is release back into the atmosphere.

Not all plant and animal bodies will decay. Some are buried under layers of silt and over millions of years begin to fossilise.

This forms fossil fules such as coal, oil and gas.

Humans extract fossil fules and burn them to release energy.

Burning fossil fuels releases the carbon that was stored millions of years ago as carbon dioxide.

In a stable environment, the amount of carbon dioxide should approximately be equal the amount absorbed.

Friendly microbes in the cycle

Microbes- involved in the process of decay in the cycle.

Two main groups involved-

Fungi     Bacteria 

The process of decay releases nutrients such as carbon back into the environment, these nutrients can then be reused by plants to grow.

Happens more at certain times at year- Autumn

As microbes have the right conditions to survive and respire:

food ( dead plants- fallen leaves)      suitable temp                         suitable ph

oxygen                                          moisture 

When conditions are poor- rate of decay slow. - Waterlogged soils, acidic soils. 

Carbon built into the bodies of plants and animals may stay there for millions of years.

In oceans there may be (intertebrate) animals with shells to protect thier bodies- shells made of calcium carbonate- animals incoporated carbon gained from digesting plants into thier shells. hen they die- shells sink to bottom of ocean- difficult to decay- fragments compressed- form rocks- turned into limestone and chalk- Oceans called carbon sinks.

Eventually carbon released- some limestone rocks become exposed above sea- limstone and chalk eroded by weathering. Carbon released back into atmosphere.