Bio geo chemical cycle can be easily understood by knowing its meanings
Bio – life (living beings)
Geo – land ,air ,water, soil part
Chemical – minerals
Cycle – path
So we can say that “Bio geo chemical cycle is basically a path through which minerals i.e. nutrients are uptaken by bio part i.e. living beings ,and again minerals are transferred to geo (soil ,air ,land ,water) part of environment.”
Bio geo chemical cycle can be of two types
1. Gaseous cycle – in gaseous cycle transfers of C, H, O, N takes place and the main source of C H O N are atmosphere and hydrosphere.
2. Sedimentary cycle – in sedimentary cycle transfers of Ca, P, S takes place. The source of Ca P S is lithosphere.
Here we will discuss Carbon, Nitrogen and Phosphorus cycles
Carbon cycle : Free carbon present in the form of CO2 in the environment. The main sources of carbon are atmosphere ,carbonate rocks ,ocean , Coal and petroleum.
Producers fix atmospheric CO2 into carbohydrate (glucose ) . this glucose is taken up by consumers , during their respiration they release CO2 in the environment. After the demise of producers and consumers ,they are decomposed by decomposers. Decomposers also release CO2 in the environment during their respiration.
Nitrogen cycle : Plants are not able to use atmospheric N2, they can take N2 in the form of nitrate. So first atmospheric N2 is converted into NH3 .this process is known as Nitrogen Fixation. This is done by the microorganisms like Rhizobium ,Nostoc ,Anabaena.
Nitrification : Ammonia is coverted into nitrite by Nitrosomonas , this nitrite is further converted into nitrate.by Nitrobacter .
Nitrogen assimilation : This nitrate is consumed and protein is made by the plants..when consumers consume the producers , protein is transferred to the consumers.
Ammonification : After the demise of the plants and consumers ,formation of litter takes place, this litter contains protein ,this protein is converted into NH3 by some bacteria like Bacillus ramosus.
Denitrification : Excess nitrate which is not used by the plants get converted into N2.
eg. Pseudomonas denitrificans.
Phosphorus cycle : The main source of phosphorus is rocks , Due to the weathering ,phosphorus is released to the soil. Producers takes this phosphorus from the soil ,and from the producers it is transferred to the consumers after the demise ,phosphorus is released to the environment.