All of the above. Animals can obtain nitrogen from plants, which they consume as part of their diet. They can also obtain nitrogen from consuming other animals. In addition, bacteria in the soil and in the guts of animals play a crucial role in the nitrogen cycle by converting nitrogen-containing compounds such as nitrites and nitrates into forms that can be used by plants and animals. Nitrites and nitrates are forms of nitrogen that can be absorbed and utilized by plants as nutrients.
