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Activity Book ONE Photosynthesis The effect of (a) light intensity (b) carbon dioxide concentration on the rate of p

Activity Book ONE Photosynthesis The effect of (a) light intensity (b) carbon dioxide concentration on the rate of photosynthesis ANSWER 2007. 7.6. Investigation of the effect of light intensity on the rate of photosynthesis.

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Activity Book ONE Photosynthesis The effect of (a) light intensity (b) carbon dioxide concentration on the rate of p

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  1. Activity Book ONE Photosynthesis The effect of (a) light intensity (b) carbon dioxide concentration on the rate of photosynthesis ANSWER 2007

  2. 7.6 Investigation of the effect of light intensity on the rate of photosynthesis 1 Why should we keep the temperatureconstant throughout the practical? Factors (e.g. temperature, supply of carbon dioxide) other thanthe one being investigated (light intensity here) can also affect the rate of photosynthesis. They must be kept constant or a conclusion cannot be drawn.

  3. 2 Why should we allow the plant to equilibrate before taking any readings? To allow time for the rate of photosynthesis to become steady, orto let the plant adjust to the new set of environmental variables.

  4. 3 Why should we take three readings? Taking the average of three readings gives a more accurate result.

  5. 4 Describe and explain the graph you have drawn. • At low to moderate level of light intensity, the rate of photosynthesis increases proportionally with (= in direct proportion to) increasing light intensity. • (To be continued.)

  6. cont. • This is because more energy is provided to the plants to carry out photosynthesis. • As light intensity increases, the increase in photosynthetic rate becomes less. • When light intensity is abovea certain level, the rate of photosynthesis does not increase with further increase in light intensity. This is because other factors such as carbon dioxide concentration become limiting.

  7. 5 Give a possible source of error in this practical and suggest a way of improvement. Error : There are other light sources. Improvement: Carry out the practical in a dark room. Other acceptable answers …….

  8. 6 Suggest another way to measure the rate of photosynthesis. Record the number ofoxygen bubbles given off per unit time. Record the total volume of oxygen evolved in a fixed interval of time.

  9. Conclusion What conclusion about the effect of light intensity on the rate of photosynthesis can you draw from this practical? The rate of photosynthesis increases with increasing light intensity. The increase stops when a certain level of light intensity is reached.

  10. 7.7 Design an investigation of the effect of carbon dioxide concentration on the rate of photosynthesis Design and perform an experiment 1 What are the controlled variables in this experiment? Temperature, light intensity, time allowed for the release of oxygen, etc.

  11. 2 What is the independent variable in this experiment? Carbon dioxide concentration.

  12. 3 How are you going to vary the independent variable? By using sodium hydrogencarbonate solution of different concentrations.

  13. 4 What is the dependent variable in this experiment? The volume of oxygen released per unit time.

  14. 5 What is the control in this experiment? An apparatus that has sodium hydrogencarbonate solution is replaced with distilled water.

  15. 6 How are you going to recordand present the results? (Answer varies with Ss.) 7 How can you obtain faster results? Provide a higher light intensity. Or, put the lamp nearer to the plant.

  16. 8 How can you make sure that the results are reliable? Allow the plants to equilibrate before taking any readings.Take the average of three readings at each concentration of solution.

  17. What precautions should be taken? • any one l Include a heat shield and check its temperature at intervals. l Make sure the apparatus is air-tight by closing the clip completely. l Don’t spray water onto the hot light bulb.

  18. Write an experimental report Objective To investigate the effect of carbon dioxide concentration on the rate of photosynthesis.

  19. 7.7 Design an investigation of the effect of carbon dioxide concentration on the rate of photosynthesis Apparatus and materials

  20. Apparatus and materials

  21. Procedure

  22. Procedure Home Back Next

  23. Results

  24. Describe and explain the results of your experiment. Analysis and discussion From 0 to 0.25% sodium hydrogencarbonate solution, the rate of photosynthesis increases rapidly with increasing carbon dioxide concentration. (To be continued.)

  25. …… continued from previous page This is because more carbon dioxide is provided to the plants as raw material to carry out photosynthesis. From 0.25% to 0.4% sodium hydrogencarbonate solution, the rate of photosynthesis slows down with increasing carbon dioxide concentration. This is because other factors such as temperature become limiting.

  26. Conclusion The rate of photosynthesis increases with increasing carbon dioxide concentration. It slows down gradually when other factors become limiting.

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