Nitrogen is a component in chlorophyll, which is essential for plants to perform photosynthesis. Nitrogen is also required to make amino acids, which are building blocks of proteins that are essential for cellular function.
Nitrogen makes up approximately 78 percent of the volume of the atmosphere. Atmospheric nitrogen does not freely combine with other elements, meaning living things cannot use it for cellular processes. Nitrogen fixing bacteria take nitrogen from the air and convert it to a type that living things can use. Plants absorb this fixed nitrogen from the soil. They then pass it on to animals when animals eat the plants.
Some plants have developed a symbiotic relationship with nitrogen fixing bacteria. These plants allow the bacteria to live in nodules on their roots, keeping a supply of usable nitrogen close at hand. Legumes are one example of a type of plant that uses this process.
To complete the nitrogen cycle, fixed nitrogen must be converted back into atmospheric nitrogen. Denitrifying bacteria conduct this process. Should too much fixed nitrogen remain in the soil, an imbalance in plant life can occur. Human interaction with the nitrogen cycle can increase undesirable effects, altering food chains and resulting in loss of biodiversity.