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Determine the effect of light intensity on the rate of photosynthesis in Eledeo.

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An investigation to determine the effect of light intensity on the rate of photosynthesis in Eledeo Introduction The process of photosynthesis is the transfer of light energy into chemical potential energy of organic molecules. An equation for photosynthesis is: i Photosynthesis is vital for existence of both plants and animals, as they are dependent on energy that is provided by the sun. 'Green plants and other photosynthetic organisms have the essential role of providing the entire input of energy to an ecosystem.'ii 'Photosynthesis in plants converts light energy to chemical energy in organic molecules. Animals eat plants, obtaining some of the chemical energy in the molecules they taken in.'iii iv In photosynthesis, there are two sets of reactions involved: -The light independent reaction (Calvin cycle), which take place in the chloroplast stroma. Its role is the fixation of carbon dioxide, which is reduced to carbohydrates, using hydrogen and water. The carbon dioxide combines with a pentose sugar to produce ribulose biphosphate (RuBP). This continues to form two molecules of a three-carbon molecule called glycerate-3-phosphate. From this, two triose molecules are created due to the presence of ATP and reduced NADP, of which some condenses to form hexose phosphates such as starch. The remainder regenerates RuBP. v I am going to concentrate on the light dependant stage of photosynthesis as I am going to investigate the effect of light intensity on the rate of photosynthesis. ...read more.


I will place my test tube with the pondweed into a beaker full of water and add cold water every time the temperature rises. To keep the surface area of the pondweed the same throughout the experiment, I will use the same pondweed, throughout the investigation. I will also allow 5 minutes for the pondweed to adjust to the environment and that is why I have timed my experiments for 15 minutes, to obtain accurate results. In an attempt to control the outside temperature, I will conduct my experiment in the dark, resulting in photosynthesis not occurring at the maximum rate. Apparatus Elodea Potometer Stopwatch Clamp Stand Beaker 15cm measuring cylinder Lamp Scalpel Thermometer Sodium Hydrogen carbonate Water Elodea is used as it enables us to see the bubbles being emitted as it is an aquatic plant. Sodium Hydrogen Carbonate stimulates photosynthesis if there are no obvious signs of bubbles being produced (this increases carbon dioxide availability). Apparatus to be set up as shown in diagram 1. Diagram 1 Safety Procedures - Potometer must be securely fixed to clamp. - Make sure that the apparatus are not close to the edge of the table - When conducting the experiment, do not sit down as the apparatus may fall on you - Do not consume any of the chemicals - Make sure that all bags and coats are put away tidily - All spillage's must be cleaned up ...read more.


There are no more electrons that can be excited and no further ATP can be synthesised. The light intensity of light on a given object from a constant source, in this case the spot light, is inversely proportional to the square of the distance between them so: Intensity = I/d2. By observing the results table and graph the optimum temperature, light intensity seems to be 0.01. Statistical analysis was done by using Pearson's product moment correlation co efficiency. The statistical test shows the strength of the relationship between the independent and dependant variable. By observing the graph, an anomalous result can be identified, as it does not fit on the line of best fit. This anomalous result may be due to fact that some of the oxygen that was meant to obtain dissolved into the water and the Elodeo stem not placed completely up the collecting tube so some of the oxygen was lost. The level of significance, which is 1% for the tailed hypothesis, has a value of 0.93437. The value obtained in this experiment was less than 0.93437. However 2.5% results will be due to chance as the value at 2.5% is 0.8783 and the value obtained in this experiment is greater than that. ix x i Cambridge Advanced Sciences Biology 2 Chapter 2 Page 17 ii Cambridge Advanced Sciences Biology 1 Chapter 7 Page 94 iii Cambridge Advanced Sciences Biology 1 Chapter 7 Page 93 iv Cambridge Advanced Sciences Biology 1 Chapter 7 Page 94 Figure 7. ...read more.

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