Biogeochemical Cycles (Nutrient Cycles) ❧ ❧In terms of matter, Earth is a closed system ❧Nothing enters or leaves, just recycled ❧This is the Law of Conservation of Matter! ❧ Matter is neither created nor destroyed, but recycled and reused ❧Important cycles: carbon, oxygen, nitrogen, phosphorus, water Carbon Cycle = process where C is cycled b/w atmosphere, land, water, & organisms (during photosynthesis & cellular respiration) ❧ Steps: How Humans Affect the Carbon Cycle ❧ Burn fossil fuels → releases CO2 into atmosphere ❧ More CO2 in atmosphere causes global warming through greenhouse effect How You Can Reduce Your Carbon Impact: ❧Use gas-efficient cars ❧Carpool/ use public transportation ❧Walk or ride bike when possible ❧Eat locally-grown food ❧Use less plastics & disposable products Oxygen Cycle = process where oxygen is cycled b/w atmosphere, ocean, & organisms ❧ All organisms need Oxygen 1. Producers release O2 during photosynthesis ❧CO2 + H2O + sun → C6H12O6 + O2 2. Organisms use O2 during cellular respiration ❧ C6H12O6 + O2 → CO2 + H2O + energy 3. O2 is stored: ❧Dissolved in oceans ❧Oxygen in the atmosphere: ❧ O2 is 21% of lower atmosphere ❧ Ozone (O3) in upper atmosphere protects us from UV rays Nitrogen Cycle = process where nitrogen (N) is cycled b/w atmosphere, bacteria, & other organisms ❧ All organisms need N for proteins & nucleic acids (DNA) 1. N2 gas must be changed by nitrogen-fixing bacteria: ❧ They convert N2 into nitrates (NO3) 2. Plants get NO3 from soil → animals eat plants 3. Plants & animal waste puts N back into soil in form of ammonia (NH4) 4. Other bacteria convert ammonia into nitrites (NO2) & nitrates Nitrogen Cycle How Humans Affect the Nitrogen Cycle ❧Have doubled amount of N on land due to use of fertilizers & burning fossil fuels ❧Problems of too much N: ❧ Rivers & lakes becoming acidic ❧ Global warming Hydrologic (Water) Cycle = path of H2O through environment ❧ Most H2O is stored in oceans ❧ Ocean H2O is turned to vapor (gas) by evaporation & winds push vapor around globe ❧ H2O vapor turns to liquid in atmosphere = condensation ❧ Liquid falls as precipitation (rain, snow, etc.) ❧ Living organisms use H2O, then return it to environment through: ❧ Breathing & sweating ❧ Waste ❧ Transpiration from leaves (plants) (leaves sweating) ❧ Water Cycle ❧ How Humans affect the Water Cycle: ❧ ❧Remove H2O faster than nature can replace it ❧Drain wetlands → increases flooding ❧Pollution Phosphorus Cycle = movement of phosphorus (P) between environment & organisms ❧P is important in DNA and ATP Steps: 1.Rocks erode, putting phosphate into soil and water 2. P is taken up by plants & converted to organic molecules 3. Animals eat plants 4. Decomposing plants & animals & waste return P to environment ❧How humans affect P cycle: ❧ Excess phosphate from fertilizers can cause too much algal growth in water → kills fish & other organisms Phosphorus Cycle ❧ Excess P due to fertilizers!