Stability may be defined by the ecosystem's inertia , or ability of an ecosystem to remain on one trajectory without deflection. Stability may also be defined by an ecosystem's resilience , or ability to return to its original state following disturbance. The actual assemblage of organisms within ecosystems can vary greatly even though one has a single type of ecosystem, such as the rainforest biome. Hence, to begin classifying the earth's ecosystems, we use those ecosystems that are structurally similar, achieved under specific climate conditions . It is climate that largely determines the assemblage of plant and animal species that can live in an area.
Climate varies by latitude due to two reasons.
First, the angle of incidence changes as one moves from the equator to the poles, causing the amount of insolation to become spread over greater areas as one moves poleward. Second, climate varies due to the movement of air masses and ocean currents as the Earth tries to achieve a balance of energy resulting from a surplus at the equator and a deficit at the poles. Atmospheric circulation takes the form of Hadley cell circulation causing a latitudinal sequence of high and low pressure areas. Climate patterns are further complicated by the Coriolis effect , which is a result of the Earth's rotation, causing all fluids in the Northern hemisphere to be deflected to the right, and all fluids in the Southern Hemisphere to be deflected to the left. The Coriolis force is strongest at the poles where one experiences maximum spinning, and weakest near the equator.