Essential nutrients
a. are made by the body
b. can only be supplied adequately with dietary supplements
c. must be obtained through diet
d. consist of over 75 different types of nutrients

it's c.us forest service

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.

that's all i luck!