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What affects the rate of photosynthesis in Elodea?

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Biology Coursework What affects the rate of photosynthesis in Elodea? Aim: To find out which factors affect the rate of photosynthesis in Elodea. Variables: The variables that might affect the rate of photosynthesis in this experiment are: Temperature: When the temperature rises so does the rate of photosynthesis; this is because as the temperature around the plant rises the enzymes controlling photosynthesis inside the chloroplasts heat up and start moving around faster, the fast moving molecules collide with other fast moving enzymes causing them to react. The rate of diffusion of carbon dioxide into the leaves will also ride as temperature does. This happens because fast moving carbon dioxide molecules will hit the surface of the leaf far more often than in a colder atmosphere therefore more molecules will be taken into the leaf and diffusion will happen faster. However, the rate of photosynthesis will only keep on rising until the temperature reaches 45'c at that temperature the enzymes in the chlorophyll will be destroyed and photosynthesis will stop all together. On the other hand, if the temperature is too cold then temperature will become the limiting factor and the enzymes will stop working. Carbon dioxide: The amount of carbon dioxide in the atmosphere around the elodea affects the rate at which it will photosynthesise. The plant needs carbon dioxide to react with water molecules to make glucose. If there isn't enough carbon dioxide for the plant to take in the plant wouldn't have enough glucose or food and would die. ...read more.


The ruler needs to be straight from the boiling tube to the lamp. I will attach a paper clip firmly to the end of my elodea and place my piece of elodea into the boiling tube I will carefully cut the end of my elodea using a pair of scissors, making sure that it is kept under the water at all times. To make sure that the light intensity is entirely controlled by me I will turn off all the room lights and cut off any other major light sources. When my experiment is set up correctly I will make sure my lamp is lined up at 10 cm and turn it and the stop watch on at exactly the same time. I will then time the 2 minutes whilst counting the bubbles carefully and recording the measurements and the number of bubbles per 2 minutes. I will repeat this experiment 6 times changing nothing but the distance the light is away from the Elodea. The distances will be 10cm 20cm 30cm 40cm 50cm 60cm 70cm and 80cm. To get more accurate results I will repeat the experiment 3 times if possible Predictions: Using my scientific knowledge and the research that I have been doing I would predict that light intensity will affect the rate of photosynthesis in this way: The closer the lamp is to the elodea the stronger the light intensity will be, I know this because we have being doing tests to measure the light intensity using specialist equipment. Our findings from this are that the brighter the light or the closer the light, the stronger the light intensity. ...read more.


It is more likely that the similar anomalies results are due to faults the equipment that was used because we used exactly the same equipment each time. It could also be due to light coming from other sources to our experiment causing the rate of photosynthesis to rise with the light coming in though I do not know however how this could have happened in all 3 experiments. My prediction was fairly similar to the results that I got from my investigation. Conclusion Although there is a clear pattern in my experiment, as I have mentioned before, the evidence I obtained hasn't corresponded with research and other sources of information that has been found. This makes me uncertain of how accurate my results are and therefore causes me to think that the results that I have obtained are not exact enough to prove my hypothesis. The experiment was simply not carried out with enough attention to detail. This experiment could most defiantly be improved. More elodea in a larger water holder would have been better and produce many more bubbles and getting better results. The light could have been a lot brighter so, again, we would get more bubbles, and also the range of distance of which we measured could be increased. For further results, we could have tested how temperature affected the plants along with testing how carbon dioxide levels affected photosynthesis. We would achieve temperature with usage of electric heaters and thermometers and carbon dioxide by putting bottles over the plant. In summary, this whole experiment could and should have been redone, we more care, thought and better equipment. ...read more.

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