2Why is Nitrogen Important? All organisms require nitrogen to live and build proteinsWhere is it found?Free nitrogen gas 78% of atmosphereIn wastes, produced by organismsIn dead and decaying organismsOrganisms must convert it to another form to use it
3Nitrogen FixationNitrifying bacteria change free N2 gas into nitrogen compounds that can be used by plantsPlants use them to make plant proteinsAnimals eat the plants and use the proteins to make animal proteinsWhen plants and animals die, nitrogen compounds return to the soil
4DenitrificationDenitrifying bacteria in the soil break down these nitrogen compounds into free nitrogen, which is returned to the atmosphere
5Nutrient CyclesNutrients that are available in fixed quantities on Earth are passed from one organism to another and from one part of the biosphere to another.The amount of nutrients does not change, but the form might.