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How temperature affects the rate of photosynthesis.

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Biology A2 Coursework How temperature affects the rate of photosynthesis Contents: Title: Page number: Abstract Introduction Preliminary experiment Aim Prediction Apparatus Diagram Method Key variables Safety Results Graph (individual) Graph (class) Statistical analysis (t-test) Conclusion Discussion Evaluation Bibliography Abstract: The aim of the experiment was to observe and analyse the affect of temperature on the rate of photosynthesis. This rate was measured by the rate of oxygen produced (mm3/min), by a photosynthesising plant (elodea), under different temperatures. A specialised apparatus called a potometer was used to observe this affect. A certain length of elodea (50mm) was cut at a slant at one end, and was placed in a test tube and was immersed in the pondweed water it was accustomed to. The cut end of the elodea was attached to a delivery tube which was connected to a measuring tube which was further attached to a syringe by rubber tubing. This whole apparatus (the potometer) was then placed in varying temperatures to measure the affect of the temperatures on the rate of oxygen production. For each temperature the length of the oxygen bubble released by the plant was measured by pulling it into the measuring tube of the potometer by using the syringe. This length was recorded and converted to the rate of oxygen produced by the plant per minute under that temperature (mm3/min). The same elodea was used to perform the experiment under the same temperature three times all together i.e. there were three repeats for each temperature. The temperatures used were: 0 oC, 15 oC, 25oC, 35 oC, 45 oC, 55oC, and 65 oC. Many factors affect the rate of photosynthesis mainly carbon dioxide concentration (controlling the rate of the Calvin cycle), light intensity (Affecting the light stage) and temperature (affecting the kinetic energy of all the molecules, including enzymes involved in the photosynthetic reactions and reducing the rate of photosynthesis by denaturing the enzymes after a certain temperature). ...read more.


Goggles again should be worn while pouring elodea water into test tubes which again should be done using a pipette. Tweezers should be used and gloves should be worn while using tweezers to pull the elodea out of the pondweed water to avoid any contact of the water with bare skin. * The light source i.e. the lamp should be kept at a safe distance from water or any other liquid apparatus to prevent electrocution or malfunctioning of the lamp. The same applies for any other electrical equipment like the digital clock because it can stop working if it comes in contact with a liquid. Additional precautions should be taken while handling the light source because gradually it will get heated and carries a danger of burning skin if handled incorrectly. * Care should also be taken while handling sharp instruments like the scalpel to prevent any physical injuries. Results: Table showing the results obtained from the experiments conducted individually at different temperatures: Repeat Temperature (oC) Light Intensity (LUX) A-Lowest H-Highest Length of O2 released in 5 mins (mm) Volume of O2 released in 5 mins (mm3/5mins) Rate of O2 released (mm3/min) Average rate of O2 released (mm3/min) 1 H 0.00 0.00 0.00 2 0 H 0.00 0.00 0.00 0.13 3 H 1.00 2.01 0.40 1 H 5.00 10.05 2.01 2 15 H 3.00 6.03 1.21 1.61 3 H 4.00 8.04 1.61 1 H 60.00 120.64 24.13 2 25 H 70.00 140.74 28.15 27.48 3 H 75.00 150.75 30.15 1 H 100.00 201.06 40.21 2 35 H 130.00 261.38 52.28 47.58 3 H 125.00 251.33 50.27 1 H 160.00 321.70 64.34 2 45 H 123.00 247.31 49.46 58.71 3 H 155.00 311.65 62.33 1 H 8.00 16.08 3.22 2 55 H 6.00 12.06 2.41 3.22 3 H 10.00 20.12 4.02 0.00 1 H 2.00 4.02 0.80 2 65 H 6.00 12.06 2.41 2.14 3 H 8.00 16.08 3.22 Class Results: Table showing the individual average results and the class average rate of oxygen production at each temperature: Temperature (oC) ...read more.


If possible a measuring tube accurate to 1decimal place can be provided for more accurate results. * A digital light intensity meter can be use instead of an analogue one. A digital light intensity meter would provide us with information on a slight change in the light intensity. Even if the light intensity cannot be kept constant during the experiment, having accurate information on how it changed would lead to better and more accurate conclusions from the results. * To record any changes in the temperature of the apparatus, instead of using a thermometer, a data logger attached to a temperature sensor can be used. It will record any changes in the temperature throughout the experiment. These changes will be more accurate and far more accurate changes to the temperature can be made as required. * For more accuracy, a digital clock with a higher degree of accuracy (say correct to 0.001 seconds) can be used which would provide more accurate timing throughout the experiment. * For more accuracy the same elodea plant should be used throughout the experiment as the number of leaves or the surface area of the plant will not be a limiting factor. To achieve this, firstly human errors will have to be eliminated in preparing the elodea plant i.e. cutting the shoot at an angle and measuring the length exactly. Then the experiment should be carried out in increasing order of temperatures i.e. starting from 0 oC and finishing at 65 oC. To prevent the risk of enzymes in the elodea being inactive and denatured after a high temperature like 55 oC which would cause the same elodea to be unavailable to be used for 65 oC, less number of temperatures with a higher number of repeats can be used. These temperatures can be much closer together, for instance at a difference of 5 oC each instead of 15 oC. So the experiment temperatures can be 10 oC, 20 oC, 30 oC, 40 oC, 50 oC with 4 repeats each. ...read more.

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