<span>A. If one essential nutrient within an ecosystem runs out, primary productivity will be limited.
A specific nutrient is need for every organism in the ecosystem. If this particular nutrient is diminished within the ecosystem then cellular processes will decreases and a great number of specie will die. </span>
The variables in a study of a cause-and-effect relationship are called the independent and dependent variables. The independent variable is the cause. Its value is independent of other variables in your study. The dependent variable is the effect.
D. regulates which materials enter and leave the cell
