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❧❧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
Biogeochemical Cycles (Nutrient
Cycles)
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
❧ All organisms need Oxygen1. 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
Oxygen Cycle = process where oxygen is cycled b/w atmosphere, ocean, & 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 = process where nitrogen (N) is cycled b/w atmosphere, bacteria, & other organisms
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
❧ 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)
Hydrologic (Water) Cycle = path of H2O through environment
❧
❧ Water Cycle
❧❧Remove H2O faster than nature can
replace it❧Drain wetlands → increases flooding❧Pollution
How Humans affect the Water Cycle:
❧P is important in DNA and ATPSteps: 1.Rocks erode, putting phosphate into soil and water2. P is taken up by plants & converted to organic molecules3. 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 = movement of phosphorus (P) between environment & organisms
❧
Phosphorus Cycle
Excess P due to fertilizers!