I understand the cycle of hydrology when it illustrates the changing state of water. For an example, if wolves didn't arrive in the Black River watershed, then anyone living near there wouldn't have drinking water and is forced to live somewhere else since the deer could be staying in the Black River watershed. If the wolves didn't arrive, the watershed will still be empty and drained of water with the deer lurking around.
The air above Earth's surface.
Composed of all Earth's water.
Consists of all living things, including people.
The rigid outer part of earth, consisting of the crust and upper mantle.