Nutrient Cycles
What are the processes and features of the water cycle?
The water cycleglossary term (opens in a new window) involves the movement of water between land, bodies of water, and the atmosphere.
- The water cycle includes three major processes: precipitation, condensationglossary term (opens in a new window), and evaporation.
- Precipitation is the process of water falling from the atmosphere toward Earth’s surface in forms such as rain, sleet, or snow.
- In the water cycle, evaporation is the process of water transforming from a liquid to a gas called water vapor.
- In the water cycle, condensation is the process of water vapor cooling and changing into a liquid.
- Groundwater may form as underground aquifers, where it can be retrieved.
- Surface water collects in rivers, lakes, and other bodies of water via watersheds.
- About 97% of all of earth’s water is stored in the oceans.
What are the processes and features of the carbon cycle?
The carbon cycleglossary term (opens in a new window) involves the transfer of carbon from a gas to organic compounds.
- Carbon is the primary organic molecule on Earth, present in all living organisms.
- Carbon is cycled in various forms between the air, water, land, and organisms through many processes.
- The processes of the carbon cycle include respiration, combustion, decomposition, photosynthesis, erosion, and deposition.
- Plants convert CO2 gas into organic carbon molecules that autotrophs use as food.
- Organisms release CO2 into the atmosphere through respiration.
- Soil erosion and deposition also release carbon compounds into ecosystems.
- Decomposition of organic material releases carbon compounds into soil and into the atmosphere as CO2.
- Combustion of fossil fuels contributes to increased levels of CO2 into the atmosphere.
What are the processes and features of the nitrogen cycle?
Nitrogen is an essential element in living organisms. It is found in nucleic and amino acids.
- N2 gas is not a usable form of nitrogen for most living organisms.
- Bacteriaglossary term (opens in a new window) are responsible for converting N2 gas into usable, organic nitrogen-containing compounds. This process is called nitrogen fixation.
- Plants absorb usable nitrogen compounds from soil and animals eat the plants.
- Plants and animals return nitrogen compounds to soil through waste and decomposition.
- Mineralization is the conversion of organic nitrogen compounds to ammonium, an inorganic form of nitrogen.
- Nitrification is the conversion of ammonium to nitrate.
- Denitrification is the conversion of nitrate to N2 gas via anaerobic respiration.
- Excess nitrogen from heavy soil fertilization upsets the nitrogen cycleglossary term (opens in a new window) and can harm plants and other organisms.
What are the processes and features of the phosphorus cycle?
Phosphorus necessary for life as it is part of nucleic acids, ATP, and helps form animals’ bones and teeth:
- Large amounts of phosphorus are deposited as phosphorus compounds on the ocean floor and contained within oceanic rock.
- Phosphorus is transferred mainly in the form of phosphate (PO43-) between soil, rock, water, and organisms.
- Rock weathering is the main source of phosphorous compounds to an ecosystem.
- Plants absorb phosphorus compounds and animals obtain it from food.
- Plants and animals return phosphorus compounds to soil through waste and decomposition.
- Over-fertilization can provide soil and water with too much phosphorus, leading to excessive algae growth and altering the phosphorus cycleglossary term (opens in a new window).
