❧ ❧ 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.

❧❧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!