The document summarizes several natural cycles: 1) The carbon cycle involves carbon sinks like plants, forests and soil that absorb carbon, and carbon sources like combustion, respiration and decomposition that release carbon. 2) Nitrogen fixation converts inert nitrogen gas into bio-usable forms through atmospheric fixation by lightning or biological fixation by microbes and plants. Nitrification converts ammonia into nitrites and nitrates which plants can use but are soluble and can leach from soil. 3) The hydrological cycle describes the continuous movement of water above, on and below the Earth's surface, with the same amount of water circulating but individual molecules coming and going quickly.

1. Ecology Review Natural Cycles

2. Cycles Carbon Cycle Nitrogen Cycle Water Cycle

3. The Carbon Cycle

4. Sinks & Sources Carbon Sinks Places that absorb more carbon than they release Plants (photosynthesis) Forests Soil Carbon Sources Places or things that release more carbon than they absorb Combustion Respiration Decomposition

6. Nitrogen Fixation Conversion of Inert N 2 into bio-usable forms atmospheric fixation by lightning biological fixation by certain microbes alone symbiotic relationship with some plants and animals industrial fixation – Haber Process

7. Nitrification Nitrification – whatever form of ammonia is applied to the soil, it must be converted to be used by plants NH 3 + Nitrosomonas -> NO 2 NO 2 + Nitrobacter -> NO 3 NO 3 Very soluble form Only held loosely by soil colloids (clay & humus) ~ 5% of NO 3 dissolves in water and is lost by leaching

8. Hydrological Cycle

9. Hydrological Cycle Describes the continuous movement of water on, above, and below the surface of the Earth Individual water molecules can come and go in a hurry, but there is always the same amount of water on the surface of the earth.