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 Day 7 *

Carbon Cycle = process where C is cycled b/w atmosphere, land, water, & organisms (during photosynthesis & cellular respiration) Steps: Day 7 *

How Humans Affect the Carbon Cycle Burn fossil fuels → releases CO2 into atmosphere More CO2 in atmosphere causes global warming through greenhouse effect Scientists have been able to piece together a picture of the Earth's climate dating back decades to millions of years ago by analyzing a number of surrogate, or "proxyScientists have been able to piece together a picture of the Earth's climate dating back decades to millions of years ago by analyzing a number of surrogate, or "proxy," measures of climate such as ice coresScientists have been able to piece together a picture of the Earth's climate dating back decades to millions of years ago by analyzing a number of surrogate, or "proxy," measures of climate such as ice cores, boreholes, tree rings, glacier lengths, pollen remains, and ocean sediments, and by studying changes in the Earth's orbit around the sun. *

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 Day 7 *

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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 Day 7 *

Nitrogen Cycle Day 7 *

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 Day 7 *

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) Day 7 *

Water Cycle Day 7 *

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 Day 7 *

Excess P due to fertilizers! Phosphorus Cycle Excess P due to fertilizers! Day 7 *