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The aim of this experiment is to find out which side of a tree the most Pleurococcus grows upon, and why this is so.

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Aim The aim of this experiment is to find out which side of a tree the most Pleurococcus grows upon, and why this is so. Prediction I think the most Pleurococcus will grow on the North side of the tree. I think this will happen because, the south side of the tree receives the most sunlight. The heat from this sunlight would dry out the Pleurococcus, which would cause it to dry out, and die. As Pleurococcus is an algae, it photosynthesises. This means it needs water as is shown in the photosynthesis equation below. Water + Carbon Dioxide Oxygen + Glucose (aq) (g) (g) (s) 6H20 + 6CO2 6O2 + C6H12O6 (aq) (g) (g) (s) If it can not photosynthesise, it will not have enough energy to grow, reproduce, respire, and repair, it will, therefore, die. The other input into photosynthesis, is Carbon Dioxide, because Carbon Dioxide is a gas, and diffuses, it will not affect our experiment. The other thing that Pleurococcus needs to photosynthesise, is sunlight. Even in the North, there is enough sunlight for it to photosynthesise. The sunlight in the North is not enough to dry it out, because Pleurococcus has heavy cell walls, which prevents excessive water loss. Fair test To ensure this is a fair test, I will be measuring 10 different trees, instead of just one. ...read more.


62.5 75 90.325 5.6 2 65 65 90.75 7 3 45 60 94.025 6.3 4 53.75 85 90.7 10.7 5 16.25 35 90.625 5.3 6 46.25 85 90.625 5.3 7 42.5 70 96.2575 4.23 8 53.75 40 94.175 2.3 9 36.25 65 94.025 4.3 10 17.5 35 95.075 3.2 Analysis The graphs 1,2 and 3, and my table of averages, show that the most Pleurococcus grows on the North side of the tree. This fits with my prediction. However, I stated in my prediction that the "south side of the tree receives the most sunlight" this was not so at the time of day when I carried out my investigation. At this time of day, there was the highest light intensity in the East and West, and the lowest light intensity in the South. I think this was because during the day, as the Earth rotates about its axis, the Sun appears to move across the sky, in a curved arc. This arc leans towards the East, this means that during the period of a day, the North side receives the least sunlight. At midday, when I carried out my experiment, the range in light intensity averages between the different compass points was less than 3%, this was because I took my readings at midday, when the sun is between the East and the West, and is overhead. ...read more.


Therefore, if I did the experiment again, I would try to eradicate some of these problems. For example, I would choose an area with larger spacing between the trees, thus ensuring that the effects of exposure etc, were more universal. I would measure all the circumferences of the tree trunks, and, using this data, select 10 of a similar size. To gather more data, I would measure more trees, and measure from all eight compass points, to give me more data. I would use a larger quadrat, with smaller squares, to ensure a higher degree of accuracy. I would also measure humidity at hourly intervals throughout the day, to investigate my theory that Pleurococcus does not grow in the lightest areas because it is too dry. I would use a sunlight hour measurers, set up at each compass point of the tree, to see how much sunlight the side of the tree received in a day. This would make my experiment more inaccurate. Further experiments I could carry out, to research more into Pleurococcus, could include measuring: * Different types of trees and the amount of Pleurococcus on them * Measuring how pollution affects amount of Pleurococcus * Testing different sites to see where the most Pleurococcus grows * How size of tree affects amount of Pleurococcus * What height the most Pleurococcus grows * Investigate the other surfaces Pleurococcus grows upon * Investigate other plants to find if other plants are affected by which compass poitn they face ...read more.

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