6. Tetrahymena is a protozoan that lives on the skin, eyes, and muscles of guppy fish it causes lesions in the eye and a condition known as "popeye." Which best describes the relationship between and
guppy fish?
A commensalism
B mutualism
C parasitism
D predation

the correct answer is:

a population changes in response to a change in the environment.

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.