Vance is demonstrating conceptual knowledge
Conceptual knowledge is the clear and detailed understanding of principles, concepts, models or theories and the understanding of the linking relationships between them. Conceptual knowledge is acquired by thoughtful, reflective learning, listening, reading, or viewing. From the question, Vance is demonstrating conceptual knowledge because he has the explicit understanding of why rainfall amounts affect different types of vegetation positively and others negatively.
Troposphere should be the answer
scientists can test differences of the area with pigmentation by observing which is lighter and which is darker however they use microscope to look the difference of the pigmentation over the cells.
One affects radicle (root) growth while the other affects plumule shoot growth.
I would say immigration only.
emigration would theoretically reduce the genetic variation as unique individuals leave, but immigration would bring unique traits into circulation in an ecosystem.
I'm not super great at biogy tho so this might not be right... :)
