When we talk about soil quality we talk about soil components. The chemical composition is an active part of the soil components because it has Nitrogen, Ca+, Oxygen and other molecules that affects the interaction among the soil and its environment. The living organisms interacts with the molecules in the soil changing constantly their concentrations that modify the pH and the soil quality. All of these changes accumulation tell us how the soil has changed through the time, also can give us information to predict how soil will change, this is known as history of the soil.
To summarize the chemical composition affects directly the soil quality, the history of the soil are all the changes that it has suffer in its composition through time so it define the actual soil quality and the living organisms interact with the chemical composition changing it constantly and giving new qualities to the soil.
20 percent available at the highest tropic level. There is less at the top of the food chain because it has ate things from possibly all areas of the food chain and each level is consuming from lower parts of the chain than it. So with the entire food chain eating on what the top eats there is gonna be less for the top
Based on the scenario being described within the question it can be said that the type of trial that she has joined is known as a double-blind study. This is a type of study in which individuals are chosen randomly for each clinical intervention and the results are not given to the researchers until after the trial. This also includes any and all information that may influence the researchers behavior or thoughts on the study.