1. Ecology ‣ Ecology is the study of the relationships between organisms and their physical and biotic environment: Relationships involve interactions with the physical world as well as interrelationships with other species and individuals of the same species. O2O2 Nutrients CO 2

2. ‣ Living organisms can be studied at different levels of complexity. ‣ From least to most complex, these levels are (in an ecological context): Individual Population Community Ecosystem Biome Biosphere Biological Complexity Biosphere Biome Ecosystem Community Population Individual

3. ‣ Carbon cycles between the living (biotic) and non-living (abiotic) environments. Gaseous carbon is fixed in the process of photosynthesis and returned to the atmosphere in respiration. Carbon may remain locked up in biotic or abiotic systems for long periods of time, e.g. in the wood of trees or in fossil fuels such as coal or oil. Humans have disturbed the balance of the carbon cycle through activities such as combustion and deforestation. Processes in Carbon Cycling Burning fossil fuels Petroleum

4. The Carbon Cycle

5. ‣ Nitrogen cycles between the biotic and abiotic environments. Bacteria play an important role in this transfer. Nitrogen-fixing bacteria are able to fix atmospheric nitrogen. Nitrifying bacteria convert ammonia to nitrite, and nitrite to nitrate. Denitrifying bacteria return fixed nitrogen to the atmosphere. Atmospheric fixation also occurs as a result of lightning discharges. ‣ Humans intervene in the nitrogen cycle by producing and applying nitrogen fertilizers. Nitrogen in the Environment

6. Nitrogen Transformations ‣ The ability of some bacterial species to fix atmospheric nitrogen or convert it between states is important to agriculture. Nitrogen-fixing species include Rhizobium, which lives in a root symbiosis with leguminous plants. Legumes, such as clover, beans, and peas, are commonly planted as part of crop rotation to restore soil nitrogen. Nitrifying bacteria include Nitrosomonas and Nitrobacter. These bacteria convert ammonia to forms of nitrogen available to plants. NH 3 NO 2 - NO 3 - NitrosomonasNitrobacter Root nodules in Acacia Nodule close-up

7. Nitrogen Cycle

8. The Phosphorus Cycle Guano deposits

9. Sulfur Cycling Sulfur is an essential component of proteins and is important in determining the acidity of precipitation, surface water, and soil. Sulfur circulates through the biosphere as: hydrogen sulfide (H 2 S) sulfur dioxide (SO 2 ) sulfate (SO 4 2- ) elemental sulfur (S) Human activity releases large quantities of sulfur through: combustion of sulfur-containing coal and oil, refining petroleum, smelting, and other industrial processes Sulfur in petrol Molecular bridges in proteins Elemental sulfur

10. The Sulfur Cycle Sedimentation of sulfides and sulfates Organic deposition Mining Reduced sulfur (H 2 S) Decomposition and other processing Microorganisms SO 2 from combustible fossil fuels Sulfates in the atmosphere (SO 4 2- ) Inorganic sulfur Sulfur in fossil fuels Iron sulfides in deep soil and sediments Uplifting in groundwater and and weathering Uptake by plants Sulfur in living organisms Acid precipitation Sulfates in water (SO 4 2- ) Sulfates in soil(SO 4 2- ) SO 2 and sulfates from volcanoes, hot springs and biogenic activity

11. The Water Cycle Condensationconversion of gaseous water vapor into liquid water Evaporation from the ocean Evaporation Evaporation from inland lakes and rivers Evaporatio n from the land Transport overland: net movement of water vapor by wind Lakes Ocean storage 97% of total water Transpiration Transpiration from plants Rivers Water locked up in snow and ice Groundwater movement (slow) Surface runoff (rapid) Infiltration: movement of water into soil Aquifers: groundwater storage areas Percolation: downward flow of water Precipitation over the ocean Rain clouds Precipitation (rain, sleet, hail, snow, fog) Precipitatio n to land