Free nitrogen (N2) refers to the nitrogen gas that makes up about 78% of the Earth's atmosphere. This form of nitrogen is inert, meaning it is very stable and cannot be used directly by plants or animals.
Fixed nitrogen refers to nitrogen that has been chemically converted from its inert gaseous form (N2) into a usable form, such as:
* Nitrate (NO3-)
* Ammonium (NH4+)
* Nitrite (NO2-)
These forms of nitrogen can be taken up by plants and used for growth. Animals then obtain nitrogen by consuming plants or other animals.
Why is this important?
The difference between free nitrogen and fixed nitrogen is crucial because it highlights the essential role of nitrogen fixation in the ecosystem. Without nitrogen fixation, life on Earth would be impossible. Here's why:
1. Essential Nutrient: Nitrogen is a vital component of amino acids, proteins, DNA, and RNA, which are essential for all life processes.
2. Limited Availability: While free nitrogen is abundant in the atmosphere, it cannot be directly utilized by organisms.
3. Nitrogen Fixation: The process of converting free nitrogen into usable forms is called nitrogen fixation. This process is carried out by:
* Microorganisms: Bacteria, primarily those living in soil and water, are the primary nitrogen fixers.
* Industrial processes: Human activities, like the production of fertilizers, also fix nitrogen.
4. Ecological Balance: Nitrogen fixation plays a critical role in maintaining the delicate balance of the ecosystem. Insufficient nitrogen can limit plant growth and productivity. Conversely, excess nitrogen can lead to pollution problems, such as eutrophication of water bodies.
In summary:
* Free nitrogen is inert and unusable by most organisms.
* Fixed nitrogen is converted into usable forms and is essential for life.
* Nitrogen fixation is a crucial process that converts free nitrogen into usable forms and maintains the balance of the ecosystem.
