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An Investigation to Determine the Effect of the Amount of Light Available on Rate of Photosynthesis in Pondweed.

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An Investigation to Determine the Effect of the Amount of Light Available on Rate of Photosynthesis in Pondweed Aim To determine to what extent the amount of light available to pondweed affects the rate of photosynthesis. Prediction I predict that as the amount of light increases the rate of photosynthesis will increase, however, above a certain level of light, other limiting factors such as heat, carbon dioxide and available nutrients will stop photosynthesis occurring any faster, and unless these other factors are made more available, increase in light will make no difference. If light is decreased from a natural level, photosynthesis would slow and eventually stop because the equation for photosynthesis is not complete without any energy from light. Equipment Measuring Cylinder Water Pondweed Funnel Beaker Lamp Diagram Plan Firstly, a beaker will be taken and filled with water as close to room temperature as possible, to prevent the temperature from changing during the experiment, then a 5cm piece of pondweed will be laid at the bottom of the beaker. ...read more.


The pondweed should also not be allowed to move during the experiment or changing of equipment at all, because if it drifts or rotates, a different surface are could be exposed to the light, affecting the result. Each test should be timed and last for 10 minutes, at the end of the 10 minutes the volume of oxygen is measured using the reading on the measuring cylinder and recorded. Fair Test All of the possible variables in the experiment will be kept constant apart from the distance of the beaker from the light which we are testing, in this way test conditions will remain the same throughout the experiment. Variables Unfortunately there will be several unavoidable variables in the experiment beyond our control, but they should not make a significant impact on the experiment's results, these include the ambient light within the classroom changing as time goes by, and the room temperature of the classroom may change slightly. Other than those, the following variables are controlled and kept constant, apart from distance of lamp. ...read more.


Distance of the light from the beaker Control (No lamp) 50cm 40cm 30cm 20cm 10cm Number of bubbles given off Results These were the results gathered from the experiment These results are also shown on a separate graph Analysis / Conclusion The experiment showed my prediction to be correct, however it did not show my predicted stop of light making any effect on the speed of photosynthesis, this may be because the light was never intense enough to prevent it being a limiting factor during the experiment. The graph shows a steady increase in rate of photosynthesis, according to oxygen given off, as the light is brought closer to the beaker, and therefore a positive correlation between the rate of photosynthesis and the intensity of light absorbed by the plant, and ultimately that light is a limiting factor in photosynthesis. The conclusion can also be drawn that as, during the control, no bubbles were given off and therefore photosynthesis was taking place either very slowly or not at all, it is reasonable to assume then that with no light at all present, photosynthesis could not occur, despite heat and carbon dioxide being available. ...read more.

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