<span>The cycle of processes by which water circulates between the earth's oceans, atmosphere, and land, involving precipitation as rain and snow, drainage in streams and rivers, and return to the atmosphere by evaporation and transpiration is called water cycle. The first picture is a picture of the water cycle.
</span>The nitrogen cycle<span> is the biogeochemical </span>cycle<span> by which </span>nitrogen is converted into various chemical forms as it circulates among the atmosphere and terrestrial and marine ecosystems. The conversion of nitrogen<span> can be carried out through both biological and physical processes.</span>