Multicellular? or do you mean animals?
The statement that highlights and describes in detail the key features of an aquatic animal would be produce qualitative data analysis as we will describe its external features such as color size etc.
Hormones -- such as melatonin and cortisol; the former signals the body to go to bed, while the latter signals for the sleeping person to wake up -- are created by physiological changes.
Answer: all the gray squirrels that live in a forest
Explanation:
A population refers to the total number of organisms of the same species living and breeding together in a given area.
Thus, since the gray squirrels all belong to the same specie and live in a given area called forest - population is best described by the phrase "all the gray squirrels that live in a forest"