Sources: Jones, IGCSE Biology- Mackean, IGCSE Biology - Pickering, Complete Biology

1. Relationships of organismswithoneanother and withtheirenvironment

3. NUTRIENT CYCLES Carboncycle Watercycle Nitrogencycle

4. CARBON CYCLE

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.

7. WATER CYCLE

9. NITROGEN CYCLE

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.

14. POPULATION SIZE POPULATION: group of organisms of onespecies, living in thesamearea at thesame time.

16. HUMAN POPULATION GROWTH

18. HUMAN INFLUENCES ON THE ECOSYSTEM AGRICULTURE POLLUTION CONSERVATION

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.

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)

24. Greenhouseeffect:gasescontributing

31. Beta particles