Biogeochemical Cycle

What is Biogeochemical Cycle?

The natural pathway through which essential elements in living matters undergoes circulation is known as a biogeochemical cycle. The natural elements in the biogeochemical cycles flow from abiotic (non-living) components to biotic (living) components. 

Biogeochemical, as a term, refers to three aspects in each cycle. Those aspects are biological, geological and chemical. 

Importance of Biogeochemical Cycle

Biogeochemical cycles help in the regulation of natural elements that are necessary for living beings, by channelling through physical and biological phenomenon. It acts as a recycling procedure in nature. 

Types of Biogeochemical Cycles 

The types of nutrient cycles largely fall under –

  1. Sedimentary cycles 

Reservoir in sedimentary bio-geo cycle is Earth’s crust and include earth-bound elements such as phosphorus, calcium, iron and sulphur among others. 

  1. Gaseous cycles 

Reservoir in gaseous bio-geo cycle is air or ocean and include carbon, oxygen and nitrogen. 

Did You Know?

While the abundance of carbon, hydrogen and nitrogen are found in human body, these elements have low occurrence on Earth’s elemental mass. This aspect perhaps will lead you to appreciate biogeochemical cycles importance. Imagine this, the majority elements that are so critical to lives of organisms, are a minuscule percentage of the Earth’s known mass. For instance, nitrogen has only 0.03% share! 

Different Types of Cycles 

If you are wondering, “what do you mean by biogeochemical cycle?”, a brief discussion on those may help you understand. 

The biogeochemical cycle diagrams are indicated by pictorial representation. 

  1. Water cycle 

Water cycle relates to the movement through various stages such as –

  • Evaporation 

  • Condensation 

  • Precipitation 

  • Infiltration 

  • Run-off

Water is indispensable for life’s existence, and ocean plays a vital role in the cycle. Atmospheric water vapour causes precipitation for which evaporation from water surface is critical. Water cycle also plays a critical role in weather, pressure and temperature in environment. 

  1. Carbon cycle 

Carbon moves from atmosphere to living organisms and back again to the atmosphere. Plants are taken as the starting point of carbon cycle. The main stages in carbon cycle are – photosynthesis, respiration, combustion and decomposition. 

  1. Oxygen cycle 

Oxygen cycle is the movement of oxygen through atmosphere, biosphere and lithosphere. It is released through the process of photolysis. The main steps of the cycle include photosynthesis and respiration and further repetition. 

  1. Nitrogen cycle 

Nitrogen is essential for life form owing to its presence in nucleic acids and proteins. Plants absorb nitrogen through microbial transformations. The main steps involved in the cycle –

  • Nitrogen fixation 

  • Nitrogen assimilation 

  • Ammonification 

  • Nitrification 

  • Denitrification 

However, note that this is not sequential order.

  1. Sulphur cycle 

Sulphur, which is present mainly as a component of amino acid, may be found in soil as proteins. It is eventually absorbed by plants as sulphates, through a host of microbial transformations. 

The sulphur proteins convert into hydrogen sulphide (H2S) which is further broken down into sulphur in reaction with oxygen. With bacterial action, it becomes sulphate to be absorbed by plants. 

  1. Phosphorus cycle 

Phosphorus mainly passes through hydrosphere, lithosphere and biosphere. It is essential for both animal and plant growth. However, it gradually depletes in soil. In comparison to the carbon cycle, the phosphorus cycle does not pass through the atmosphere. 

Test Yourself 

i. Which element is captured by plants for photosynthesis in the course of carbon cycle?

(a) Heat 

(b) Organic carbon 

(c) Inorganic carbon 

(d) Hydrogen 

ii. CHNOPS does not include -

(a) Oxygen 

(b) Sulphur 

(c) Helium 

(d) Phosphorus

[To check your answer, see the solution mentioned at the end of the article]

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FAQ (Frequently Asked Questions)

1. What is biogeochemical cycle?

It is a type of natural cycle that facilitates the movement of naturally occurring matter within abiotic and biotic components of our existing ecosystem.

2. Define biogeochemical cycle.

Biogeochemical cycle definition – A naturally occurring cycle that takes the pathway through biotic and abiotic factors of the environment in order to facilitate the circulation of essential elements comprising of living matter.

3. Describe biogeochemical cycle.

A biogeochemical cycle is a nutrient-rich slow-moving pool passing through both abiotic and biotic components. It picks up the naturally occurring elements from the abiotic component of ecosystem and infuses those in living cells. It is a continuous rapid exchange which may be both gaseous and sedimentary.