Why are several natural zones distinguished within one geographic zone?

Natural zones do not always correspond to climatic zones, since the latitudinal location of the territory is not the only criterion that affects nature. The height and distance from the sea coast are also important, because the temperature decreases with height (even in the tropical zone at an altitude of 4000-5000 m, there can no longer be tropical forests). And remoteness from the sea affects the amount of precipitation, which, in turn, affects the type of vegetation and other living organisms.