Energy and Ecosystems

1. Energy and Ecosystems

2. Ecology • Habitat : Place where an organismlives • Population: Group of the samespecies of organismswhich live in the same place at the same time • Community: All of the differentspecies living in a habitat at the same time • Ecosystem: A self contained system of organismsinteracting, whichrecievedenergy as sunlight, and losesenergy as heat. Nutrients are recycledwithin the ecosystem. • Niche: The place occupied by an organism in the foodchain

3. Energy flow throughecosystems

4. Energylosses in foodchains

5. Energyloss in ecosystems • Not all sunlight hits a photosynthesising plant • Some sunlight isreflectedfromleaf surfaces • Some sunlight passes through the leaves and is not converted to chemicalenergy. • Somewavelengths of light cannotbeused by plants • Respiration – The building of ATP producesheat, whichislost to the surroundingenvironment

6. Food chains and foodwebs

7. Trophiclevels • Producer : Photosynthesisingorganisms (plants) produce all of the food for the ecosystem. • 1st order consumer: First animal consumer in the foodchain (herbivore) • 2ndorder consumer Second animal in the foodchain (carnivore) • 3rd order consumer animals high in the trophiclevelsoften consume foodfromlowerlevelsalso (canbe omnivores) • Detritis : Dead organisms • Decomposer : Bacteria and fungidecaydeadorganisms • Detrivores: Largerorganismswhicheatdeadorganisms

8. Productivity • Productivityis the rate atwhich plants convert sunlight to energy in an ecosystem. • It ismeasured in kilojoules per m2 per year • Gross productivity : Total energyconverted • Net primaryproductivity: Remainingchemicalenergyafter plants have suppliedtheirownneeds for repiration.

9. Matterrecycling : Nitrogencycle • Nitrogenis essential for all living organisms as a building block of proteins and nucleicacid • Most nitrogenispresent in the atmosphere 78pc. • Nitrogengasisunusableby mostorganisms, as the triple covalent bond in N2 moleculesmakesthemtoounreactive. • The mostcommonuseableform of nitrogenis in ammonia NH3 and nitrate NO3. • The conversion of nitrogengas to useablenitrogeniscallednitrogen fixation.

10. Nitrogen Fixation • Natural • Lightning in atmospherecreatesnitrogenoxidegasses by reactingoxygenwithNitrogen. Thesegassesfall to the soil in rain. Tropical ecosystemsobtain a very large amount of useablenitrogenthisway. • Nirogen fixing bacteriaie Rhizobium use an enzyme callednitrogenase. This catalaysesnitrogen to ammonia. • Rhizobium can live in soil and in the roots of legumous plants. Legumous plants have root nodules which the bacteriacan live in, and getsuppliedwith atp

11. Nitrogen Cycle

13. Synthetic • Haber proccess : This is the syntheticproccessused to makeammonia for fertilisers. It uses very large ammounts of electricalenergy, and has made it possible for farmers to producemarchlargercropyields.

14. use of nitrogen • Nitrate ions are obtainedfrom the soil by plants in theirxylem • Animalsobtainnitrogen by digesting plants, or otheranimals. Digestion breaks proteinsintoaminoacidsready to use by the animal • Denitrificationbacteriacan reverse nitrogen fixation in theirmetabolicproccesses. They are common in sewagetreatment plants and compost heaps.