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How Ecosystems Work

Learn how substances are recycled through ecosystems, including the nitrogen, carbon/oxygen, hydrogen, and phosphorus cycles. Understand the importance of these cycles and how human activities are altering them.

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How Ecosystems Work

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  1. How Ecosystems Work Ch. 5, Section 2: The Cycling of Materials Standards: SEV3a, b, c

  2. How are substances recycled through the ecosystem? Chemicals oscillate between biotic organisms & abiotic reservoirs Abiotic reservoirs- where chemical is “stockpiled” outside organism. Ex: air, water, soil, fossil fuels

  3. Why is NITROGEN important to your survival? • Comes from: proteins you eat in meat, eggs, dairy • Purpose: broken down by body to build new proteins, enzymes, & repair cells

  4. NITROGEN CYCLEEven though 78% of atmosphere is nitrogen, can’t get nitrogen by breathing in air. Blood has no ability to remove nitrogen from air you inhale. Lightning can bond with nitrogen gas in the air and add solid nitrogen to soil. NITROGEN FIXATION- Nitrogen fixing bacteria on roots of legumes (clover) take nitrogen gas out of the air and turn it into usable form for plants. ASSIMILATION- Plants store nitrogen in their body tissues Animals eat plants and obtain nitrogen. Nitrogen is used to make proteins throughout body. Plants & animals defecate or die and bacteria return nitrogen to the soil. DENITRIFICATION- Other bacteria in soil return nitrogen to the air. BACTERIA are the most important “movers” of nitrogen!

  5. How are humans altering the nitrogen cycle? • Eutrophication: • Chemical fertilizers from farms or feces from feedlots overload nitrogen in soil or water • causes algae to grow and create algal bloom. • algae overpopulate, compete, & die • dead algae decompose • decomposers that are decomposing algae use up oxygen in water • fish die • Acid Rain: • Nitric acid released from burning fossil fuel • Combines with water in atmosphere & makes acid rain.

  6. Why is CARBON & OXYGEN important to your survival? • Comes from: C6H12O6 (sugar made by plants) • Purpose: used as energy source in body. Oxygen inhaled & used to break down C6H12O6

  7. CARBON/OXYGEN CYCLE Plants and algae convert carbon dioxide (CO2) from the air or water into organic compounds (C6H12O6 - which is food) during photosynthesis. Oxygen is also released. Animals eat plants and get the carbon from C6H12O6 into their bodies. This carbon provides the body with energy. Oxygen from plants is also inhaled by animal & used to break down C6H12O6. Carbon is returned to the air or water when animals & decomposers exhale CO2. Carbon is returned to soil when decomposers break down feces and dead bodies. Carbon sinks include: Ocean Shells & bones of ocean animals Fossil fuels

  8. How are humans altering the Carbon/Oxygen Cycle? • burning EXCESSfossil fuels= more CO2 in air. • cutting down trees= less CO2 removed from air. • More CO2= more heat retained= Global warming

  9. Why is HYDROGEN & OXYGEN important to your survival? • Comes from: from H2O (water) • Purpose: used in chemical reactions in body.

  10. HYDROLOGIC CYCLE Water enters the atmosphere via a. Evaporation b. Transpiration thru plants (plants giving off water as by-product of photosynthesis) c. Cellular Respiration- water is given off as a by-product of breaking down food to store energy. Condensation- water cools and forms clouds Precipitation- clouds build and release liquid in form of rain, snow, sleet, or hail. Run Off- Water rolls off land into a body of surface water (lake, pond, stream) Infiltration- Water percolates thru soil and recharges/refills aquifer

  11. How are humans altering the Hydrologic cycle? • Cutting down trees, decreases transpiration, may change rainfall patterns • Septic tanks store waste water for some homes instead of sewer pipes. Water stored in septic tank is not immediately returned to river.

  12. Why is PHOSPHORUS important to your survival? • Comes from: from various foods you eat • Purpose: used to make ATP (energy storage molecule)

  13. PHOSPHOROUS CYCLE Phosphorus (P) stored in rocks Weathering of rocks adds P to soil. Plants take up P thru roots Animals eat plants Decomposers return P to soil. Cycle starts over @ #3. Only cycle that DOES NOT have an atmospheric stage.

  14. How are humans altering the phosphorus cycle? • Overflowing sewers can increase phosphorus levels which leads to death of water ecosystem via eutrophication. 2. Cheaper detergents may contain phosphorus, if leakage occurs, eutrophication can occur (see nitrogen cycle)

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