Collecting ducts are readily recognized in the renal medulla, as relatively large tubules lined by cuboidal epithelium, in which the epithelial cells are relatively clear (i.e., not as eosinophilic as proximal and distal tubules) and have distinct cell borders
There are many different factors, but some are: the amount of natural resources (food, water, etc.), amount of predator/prey, and availability of shelter.
