Assignment #4 Biogeochemical Cycles Mrs. McCarthy Biology Saturday, March 12, 2016

I.Ecosystems cycle materials A.All materials that cycle through living organisms are important in maintaining the health of ecosystems, but 4 substances are particularly important: 1.Water 2.Carbon 3.Nitrogen 4.Phosphorus

B. All organisms require carbon, hydrogen, nitrogen, phosphorus and sulfur in relatively large quantities. C. They pass from the abiotic environment to the biotic environment.

II. Carbon Cycle A.Carbon Dioxide is used by plants through the process of photosynthesis B.Organisms release carbon into the air as a byproduct of cellular respiration C.Additional carbon enters the atmosphere by human by the combustion (burning) of fossil fuels

III. Nitrogen Cycle A. Organisms need nitrogen to build proteins and amino acids B. The atmosphere is 78% Nitrogen gas

C. The Nitrogen Cycle has 4 stages: 1. Assimilation- the absorption of nitrogen into plant and animal compounds 2. Ammonification- production of ammonia by bacteria during the decay of nitrogen-containing urea 3. Nitrification- the production of nitrate (NO 2 - ) from ammonia (NH 4 + ) 4. Denitrification- is the conversion of nitrate to nitrogen D. The growth of plants is often limited by the available nitrate and ammonia in the soil

IV. Phosphorus Cycle A. Phosphorus is needed for nucleic acids.

V. Water Cycle Precipitation Condensation Transpiration Evaporation Subsurface Runoff Surface Runoff Accumulation