Nitrogen cycling is the process by which nitrogen moves through the environment, including the atmosphere, soil, and living organisms. It involves several key steps: nitrogen fixation, where atmospheric nitrogen (N2) is converted into usable forms like ammonia (NH3) by bacteria; nitrification, where ammonia is transformed into nitrites (NO2-) and then nitrates (NO3-); and denitrification, where nitrates are converted back into nitrogen gas, returning it to the atmosphere. This cycle is essential for maintaining ecosystem health, as nitrogen is a critical nutrient for plants and animals. Without nitrogen cycling, ecosystems would struggle to support life, as most organisms cannot use atmospheric nitrogen directly. The balance of nitrogen in the environment is influenced by human activities, such as agriculture and fossil fuel combustion, which can lead to excess nitrogen and environmental issues like water pollution.