6. CARBON CYCLE REMOVAL OF CO₂ FROM THE ATMOSPHERE PHOTOSYNTHESIS: uses light energytoconvert CO₂ intoorganiccompounds in plants. ADDITION OF CO₂ TO THE ATMOSPHERE RESPIRATION: convertscarbohydratestoCO₂ withtherelease of energy. DEATH AND DECAY: provideplant and animal material fordecomposers – bacteria and fungi. COMBUSTION: releasesCO₂ bytheburning of fossilfuels. FOSSILISATION:Thehydrocarbonfuels, such as coal and petroleum, come fromancientplantswhichhaveonlypartlydecomposedoverthemillion of yearssincetheywereburied.
11. NITROGEN CYCLE 1)PROCESSES WHICH ADD NITRATES TO SOIL Nitrifying bacteria: they use ammoniafronexcretoryproducts and decayingorganisms as a source of energy. In thisprocessthey produce nitrates. Thereis a specialgroup, thenitrogen-fixing bacteria, which can absorb N₂ as a gas fromthe air spaces in thesoil, and builditintocompounds of ammonia, which can beeasilybechangedtonitratesbyothernitrifying bacteria. Some of theselive in therootsnodulesofleguminousplants(peas,beans, clover).
12. 1)PROCESSES WHICH ADD NITRATES TO SOIL(cont) Lightning: lightningdischargesmakessome of thenitrogen gas in the air combine withoxygen, formingnitrogen oxides. Theydissolve in rain, and are washedintothesoil, wheretheyformnitrates.
13. 2)PROCESSES WHICH REMONVE NITRATES FROM THE SOIL Uptakebyplants: plantrootsabsorbnitratesfromthesoil and combine themwiththecarbohydratestomakeproteins. Leaching: as rain waterpassesthroughthesoilitdissolvesthenitrates and carriesthemaway in therun-off ortodeeperlayers of thesoil. Denitrifying bacteria: Theyobtainenergybybreakingdownnitratestonitrogen gas whichthen escapes fromthesoilintotheatmosphere.
20. POLLUTION WATER POLLUTION bysewage and chemicalwaste. AIR POLLUTION by: - sulfurdioxide. - greenhouse gases POLLUTION DUE TO PESTICIDES AND HERBICIDES. POLLUTION DUE TO NUCLEAR FALL-OUT
21. POLLUTION OF WATER: the 2 pollutantsthat reduce oxygen in water are: Fertilisers: nitrates and phosphates are addedtothesoilbyfarmers. Some are washedfromthesoilby rain intothenearestpond, lakeorriver. Thisprocessiscalledleaching. Sewage: containsanexcellentsource of organicfoodfrom bacteria, and alsocontainsphosphatesfromdetergents.
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23. AIR POLLUTION BY SULFUR DIOXIDE: contributestoacid rain. BY GREENHOUSE GASES CONTIBUTING TO GLOBAL WARMING. Carbon + O₂ -> carbonmonoxide (CO) and carbondioxide (CO₂) Sulphur + O₂ -> sulphurdioxide (SO₂) Nitrogen + O₂ -> nitrogenmonoxide (NO) and nitrogendioxide (NO₂)
