What describes the transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere?

What describes the transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere?

• A. Nitrogen Cycle
• B. Carbon Cycle
• C. Desert Pavement
• D. Karst Topography

Answer: (A)

The nitrogen cycle describes how nitrogen moves from the atmosphere into soil and living organisms, and back to the atmosphere. Nitrogen is abundant as N2 gas in the air, but most organisms can’t use it in that form. Specialized bacteria and lightning convert N2 into usable forms such as ammonium and nitrate. Plants take up these forms, and animals obtain nitrogen by eating plants. When organisms die or excrete waste, decomposers release nitrogen back into the soil as ammonium, and some of it is converted to nitrate again. Denitrifying bacteria can convert nitrates back into nitrogen gas, returning it to the atmosphere and completing the cycle. This movement of nitrogen through air, soil, and living things, and back to air, is what the nitrogen cycle describes. The other options don’t describe this transfer of nitrogen. The carbon cycle tracks carbon through the atmosphere, organisms, and rocks, not nitrogen specifically. Desert pavement and karst topography are landform features, not nutrient cycling processes.

The nitrogen cycle describes how nitrogen moves from the atmosphere into soil and living organisms, and back to the atmosphere. Nitrogen is abundant as N2 gas in the air, but most organisms can’t use it in that form. Specialized bacteria and lightning convert N2 into usable forms such as ammonium and nitrate. Plants take up these forms, and animals obtain nitrogen by eating plants. When organisms die or excrete waste, decomposers release nitrogen back into the soil as ammonium, and some of it is converted to nitrate again. Denitrifying bacteria can convert nitrates back into nitrogen gas, returning it to the atmosphere and completing the cycle. This movement of nitrogen through air, soil, and living things, and back to air, is what the nitrogen cycle describes.

The other options don’t describe this transfer of nitrogen. The carbon cycle tracks carbon through the atmosphere, organisms, and rocks, not nitrogen specifically. Desert pavement and karst topography are landform features, not nutrient cycling processes.