Q.Calculate the amount of ATP required by nitrogen fixer for the formation of 1000 molecules of ammonia. Name the specialised cell of cyanobacteria where nitrogen is fixed.

Biogeochemical cycles (nutrient cycling, or the cycling of materials) describe the continuous exchange of nutrients between organisms and their environment, essential for every organism's growth, development, maintenance and reproduction. There are two basic types: gaseous cycles, which move their element mainly through the atmosphere (oxygen, carbon and nitrogen cycles), and sedimentary cycles, which move their element mainly through solid-earth deposits (phosphorus, sulphur and calcium cycles). The carbon cycle circulates carbon between organisms and their environment, driven by the reciprocal processes of photosynthesis (pulling atmospheric CO2 into living tissue) and respiration (releasing it back); additional carbon returns to the atmosphere via burning of fossil fuels, deforestation, forest fires, volcanic eruptions and decomposition, while some is instead locked away long-term as peat, coal, oil, gas and buried sediment. The phosphorus cycle is a sedimentary cycle: phosphorus, essential to DNA, RNA, ATP, NADP and phospholipids, is scarce in the living biosphere but abundant in rock deposits, marine sediments and guano, from which weathering and mining release it into …