Nutrient cycle in environment

 BIO-GEO CHEMICAL CYCLE OR NUTRIENT CYCLE

      Bio  -    Living organism

      Geo  -    Rock, Soil, Air, Water

Chemical   -  Material or Nutrients

       Cycle   -   Path

All the types of material required by ecosystem in addition of energy, are available continuously to system through recycling. Thus there is a constant exchange of materials between the living organism and their abiotic environment through the recyling of materials. This phenomenon is called Bio-geo chemical cycle.

Note: Environment factors,e.g soil , moisture, ph, temperature etc, regulate the release of nutrients into the atmosphere.

Biochemical cycle

The following types of cycle are found in an ecosystem.

(i) Gaseous Cycle - C, H, N. O cycles. Reservoir is in the atmosphere (air) or in Hydrosphere(water).

Sedimentary cycle - P. S, Ca cycles reservoirs are in earth's crust (lithosphere).

Note : In these cycles, the bulk material remains in the inactive reservoir on earth crust like sediment of sea, or water bodies.

CARBON CYCLE

The main source of carbon is atmosphere and in hydrosphere it is rocks of carbonates. Carbon present in lithosphere in the form of coal and petroleum. The carbon released from them is present in the atmosphere in the form of carbondioxide. The green autotrophs utilize CO, from the air to synthesize food materials which is obtained by other organisms as food. Carnivores obtain their carbonic food from the herbivores. These carbonic matter produce CO, through the oxidation or respiration which dissolve in air or water and again utilized by the plants.

Carbon cycle

If we look at the total quantity of global carbon, we find that 71 per cent carbon is found dissolved in oceans.

This oceanic reservoir regulates the amount of carbon dioxide in the atmosphere.

Fossil fuel also represent a reservoir of carbon. Carbon cycling occurs through atmosphere, ocean and through living and dead organisms. According to one estimate 4 x1013 kg of carbon is fixed in the biosphere through photosynthesis annually.

NITROGEN CYCLE

Atomsphere is the only source of nitrogen 78% nitrogen is present in atmospheric air. Plants absorb nitrogen in the form of nitrate ions.

Nitrogen cycle is completed in following steps

1. Nitrogen fixation-

In this process first of all some bacteria and blue green algae converts atmospheric nitrogen in to nitrogenous,

compounds viz ammonia, amino acid or nitrate salts.

e.g. Bacteria - Rhizobium, Aerorhizobium, Azospirillum Frankia, Clostridium, Azotobacter .In several tropical grasses

Blue green algae -Anabaena , Aulosira ,Nostoc in Ilooded rice field in tropics.

Note :

(1) Azotobacter is aerobic bacteria.

(2) Clostridium is anaerobic bacteria.

(3)Symbiotic relationship where the nitrogen fixing bacteria does not penetra deep into host tissue, is known as associative symbiosis

2.  Nitrification 

Conversion of ammonia into nitrate is called nitrification.

Nitrification process complete in two steps.

Note

(a) Few quantity of nitrate comes in soil by electrochemical or photochemical process.

(b) Now few quantity of this nitrate absorb by plants.

Nitrogen cycle

3.Nitrogen assimilation -

Plants absorb nitrate from the soil and form protein. When consumers eat these plants, these plant proteins is transferred into consumer.

After the death of plants and consumers litter is formed in which protein is present.

4. Ammonification -

Protein present in litter, is converted into ammonia by some ammonifying bacteria.

e.g. Bacillus vulgaris, Bacillus mycoides, Bacillus ramosus.

5. Denitrification -

Some quantity of nitrate which is not used by plants is converted into nitrogen by denitrifying bacteria.

e.g. Thiobacillus denitrificans, Pseudomonas denitrificans

Note : Some nitrate washed out from the ecosystem through seepage.

PHOSPHORUS CYCLE 

Phosphorus is the main constituent of protoplasm, plasma membrane, bones and teeth. Main source of phos- phorus is rocks. It comes from the weathering of phosphorus containing rock in the soil. Plants adsorb this phosphrous from the soil and transfer this phosphate to animals and after the death of animals it is released again into the lithosphere by the action of decomposers.

Sometimes some of the elements like phosphorus and calcium reach into the sea through water, from where they transform into rocks. They separate from the cycle for a long time so it is also known as sedimentary cycle. But when these rocks break after sometime then this phosphorus is again made available to the sea plant or seaweeds, which pass into fish and sea birds. The excretorymaterials of birds on the rocks of sea shore is called Guano and it is a source of phosphorus.

Note :- Plants absorb phosphate from the soil in the form of orthophosphate (P0⁴3-)

Difference between Carbon and Phosporus cycle.

Atmospheric inputs of phosphorus through railfall are much smaller then carbon.

2. Gaseous exchanges of phosphorus between organism and environment are negligible.