The illustration above shows how nitrogen travels through the living and non-living parts of the Earth system.
Click on image for full size
The Nitrogen Cycle
Nitrogen is an element
. It is found in living things
. It is also an important part of non-living things like the air above and the dirt below. Atoms
of nitrogen don't just stay in one place. They move slowly between living things, dead things, the air, soil and water. These movements are called the nitrogen cycle
Most of the nitrogen on Earth is in the atmosphere. Approximately 80% of the molecules in Earth's atmosphere are made of two nitrogen atoms bonded together (N2). All plants and animals need nitrogen to make amino acids, proteins and DNA, but the nitrogen in the atmosphere is not in a form that they can use. The molecules of nitrogen in the atmosphere can become usable for living things when they are broken apart during lightning strikes or fires, by certain types of bacteria, or by bacteria associated with bean plants.
Most plants get the nitrogen they need to grow from the soils or water in which they live. Animals get the nitrogen they need by eating plants or other animals that contain nitrogen. When organisms die, their bodies decompose bringing the nitrogen into soil on land or into ocean water. Bacteria alter the nitrogen into a form that plants are able to use. Other types of bacteria are able to change nitrogen dissolved in waterways into a form that allows it to return to the atmosphere.
Certain actions of humans are causing changes to the nitrogen cycle and the amount of nitrogen that is stored in the land, water, air, and organisms. The use of nitrogen-rich fertilizers can add too much nitrogen in nearby waterways as the fertilizer washes into streams and ponds. The waste associated with livestock farming also adds large amounts of nitrogen into soil and water. The increased nitrate levels cause plants to grow rapidly until they use up the supply and die. The number of plant-eating animals will increase when the plant supply increases and then the animals are left without any food when the plants die.
Last modified May 7, 2007 by Lisa Gardiner.
Shop Windows to the Universe Science Store!
"Ready, Set, SCIENCE!: Putting Research to Work in K-8 Science Classrooms
", from the National Research Council, provides insight on the types of instructional experiences help K-8 students learn science with understanding. Check our other books
in our online store
You might also be interested in:
Everything you see around you is made of tiny particles called atoms. There are many different types of atoms, each with a special combination of protons , neutrons and electrons . These different types...more
Look up into the sky and you look through millions of air molecules, eighty percent of which are nitrogen molecules, two atoms of nitrogen bonded together. Nitrogen is found all over the planet, not just...more
Nitric acid is a very strong acid that can burn your skin. Nitric acid has nitrogen, oxygen, and hydrogen atoms in it. There is a very tiny bit of nitric acid gas in Earth's atmosphere. Nitric acid is...more
Ammonia is a kind of gas. Ammonia molecules (NH3) have hydrogen and nitrogen atoms in them. The air you breathe has a tiny bit of ammonia in it. When plants and animals die and decay, they give off ammonia....more
Chemistry is the study of matter, energy, and their interactions. Chemists study the composition of substances, their properties, and how they react with each other under varying circumstances. Indeed,...more
When you think of chemistry, do you think about mixing colored liquids in test tubes and maybe making an explosion... or at least a nice puff of smoke? Did you know that a lot of chemistry happens in Earth's...more
There is more nitrogen gas in the air than any other kind of gas. About 4/5ths of Earth's atmosphere is nitrogen gas! A molecule of nitrogen gas is made up of two nitrogen atoms. There are other molecules...more