Lower Secondary - Photosynthesis


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Lower Secondary - Photosynthesis

  1. 1.  How do plants makefood? Can plants make their ownfood?
  2. 2. Autotrophs/ Autotrophic organismHeterotrophs/ Heterotrophic organism
  3. 3. OverviewWhat is photosynthesis?How does photosynthesis takeplace?Conditions needed forphotosynthesisImportance of photosynthesis
  4. 4. Q: What would the world belike if there were no greenplants on earth??1) Eventually no oxygen2) No primary producer thusanimals starve to death.
  5. 5. blue black
  6. 6. WaterCarbonDioxideGlucose OxygenLight,Chlorophyll,Suitable temperature++WORD EQUATION FORPHOTOSYNTHESIS
  7. 7. 6H2O 6CO2C6H12O6 6O2Light,Chlorophyll,Suitable temperature++CHEMICAL EQUATION FORPHOTOSYNTHESIS
  8. 8. Process where light energy isabsorbed by chlorophyll andconverted to chemical energy,which is used to synthesiseglucose from water and carbondioxide, liberating oxygenduring the process.
  9. 9. How do we tell if Photosynthesishas taken place?Test for StarchGlucose + OxygenLight energychlorophyll(stored asstarch)Carbon dioxide + WaterUse Iodine test
  10. 10. To Test for Starch in a Leaf1.Place leaf in boiling water.To stop chemical reactions in the leaf so thatenzymes will stop converting starch to glucose.2.Place leaf in hot alcohol /ethanol.To remove the green chlorophyll(decolourisation) so the final results can beclearly seen.           Bunsenburnerturned offAlcoholturnedgreen
  11. 11. 3. Dip leaf into warm waterTo remove the alcohol onthe leaf/ to soften the leaf4. Spread leaf evenly onwhite tile. Cover leafwith iodine solution to testfor the presence of starch.5. Leaf turns blue-black ifstarch is present.Leaf turns light brown,starch is absent
  12. 12. test_for_starch_in_leaf.flvMY_FAVE_SONG__THE_PHOTOSYNTHESIS_SONG_[www.keepvid.com].flv
  13. 13. Conditions Essential for PhotosynthesisSunlightChlorophyllCarbon dioxideWaterRawmaterials
  14. 14. Blue RedBest absorbedby chlorophyllViolet Indigo Blue Green Yellow Orange RedGreenLeast absorbed/Bestreflectedby chlorophyllThat’swhy aleafappearsgreen!
  15. 15. LightIntensity CarbonDioxideConcentrationTemperature
  16. 16. Factors affecting Rate ofPhotosynthesis
  17. 17. • Keep in a darkplace for 24-48hours (1 to 2days)- any stored starchwill be converted tosugars which aretransported toother parts of theplantHow to destarch a plant?
  18. 18. • To ensure that starch isabsent from the leavesat the beginning of anexperiment, so that ifany starch is formed,then photosynthesis musthave taken placeWhy destarch a plant?
  19. 19. To find out whether sunlight isnecessary for photosynthesis
  20. 20. whitegreenbrownBlue-blackTo find out whether chlorophyll isessential for photosynthesisVariegatedleaf
  21. 21. To find out whether carbon dioxide isnecessary for photosynthesisSoda lime toabsorb CO2Sodium hydroxideto absorb CO2
  22. 22. To find out what gas is given offduring photosynthesisOxygen gasreleased fromthe cut end ofthe stem
  23. 23. To find out what gas is given offduring photosynthesisToprovideCO2
  24. 24. Why is Photosynthesisimportant?Provides food and energyfor animals (primaryproducers).Produces oxygen andremoves carbon dioxidefrom the air.
  25. 25. RESPIRATION Oxygen taken in, Carbon dioxide given out Takes place all the time in living organisms.
  26. 26. DIFFERENCES BETWEEN PHOTOSYNTHESIS  RESPIRATIONCan you differentiatebetween photosynthesis& respiration?
  27. 27. PHOTOSYNTHESIS- Takes place only ingreen plants.- Carbon dioxidetaken in,- Oxygen given out.- Glucose produced.RESPIRATION- Takes place in ALLliving organisms.- Oxygen taken in,- Carbon dioxide givenout.- Glucose required.- Energy produced.
  28. 28. Net uptake/release of gasesRate of photosynthesis > rate of respirationNet uptake of CO2 > Net release of CO2Net release of oxygen > Net uptake of oxygenRate of respiration > rate of photosynthesisNet release of CO2 > Net uptake of CO2Net uptake of oxygen > Net release of oxygen
  29. 29. Photosynthesis/ RespirationNetreleaseofoxygenNetuptakeofoxygen6 am midday 6 pm midnightXTime of dayrate of photosynthesis=rate of respirationXYrate of photosynthesis>rate of respirationZrate of respiration > rate of photosynthesis20-15-10-5 -05 -10-15-20-
  30. 30. Q: Why should you not have any greenplants in your bedroom at night?At night, green plants do notphotosynthesize due to the absence oflight. Respiration takes place and thegreen plants will compete with you foroxygen.