1. CYCLING IN THE ECOSYSTEM pp. 371-374

2. DEFINITIONS Ecosystem: an environment where the living (biotic) and non-living (abiotic) things affect one another Biogeochemical process: circulation of substances through living organisms and the environment

3. WATER CYCLE

4. Evaporation: water vapor enters the atmosphere Transpiration: evaporation of water through the leaves of plants Precipitation: water vapor that leaves the atmosphere

5. CARBON CYCLE

6. Photosynthesis: converting light energy into organic compounds Cellular respiration: breaking down organic compounds to release energy Combustion: burning of fossil fuels for energy releases CO 2

7. NITROGEN CYCLE

8. nitrogen fixation: bacteria convert nitrogen gas to usable form (ammonia) ammonification: decomposers break down proteins/nucleic acids to ammonia nitrification: bacteria convert ammonia to nitrates (fertilizers) assimilation: plants take up nitrates to make proteins denitrification: bacteria return nitrogen to atmosphere

9. PHOSPHORUS CYCLE

10. Weathering: Erosion of rocks Decomposition: breaking down organic compounds Absorption: Plants absorb phosphates from soil and water Runoff: Phosphates from fertilizers or soaps washes from land into water bodies