1. Steps of the Phosphorus Cycle

2. Phosphorus Is a limiting factor in soils and streams –Is an important component of DNA, RNA, and ATP – the molecule cells use to get energy –Organisms can’t grow/function without Phosphorus When you have too much = pond scum Basically a one-way street (because of time scales and element properties, etc.) Phosphorus is NEVER in the atmosphere

3. Sulfur Cycle The Sulfur Cycle contributes to acid rain

4. Reservoir Reservoir: pool of stock of material source (emits), sink (takes in), can be both Flux: rate of transfer between reservoirs per unit time Average residence time: time taken for material to cycle through system average residence time = total size of reservoir/rate of flow short residence time: small reservoirs, high transfer rates, easy to impact long residence time: large reservoirs, slow transfer, slower to change