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Introduction

COMPARATIVE INVESTIGATION LAB ON LICHENS Design Research Question: Is there a significant difference calculated by the t-test to show that the percentage coverage of lichens found on the north side of the trees after one meter from the base of the tree be affected by the tree being either in the shaded or the sunny area? Variables: Dependent variable: - the number of lichens found on the trees. Independent variable: - trees found in the shaded areas and trees found in the sunny areas. Constant variable: - lichens found on the North side of the tress - lichens found after one meter from the base of every tree - the altitude at which the trees are looked at - the same soil type for all the trees - the surface of the trees not being too rough and very similar - the humidity of the area from where the trees are looked at - almost the same amount of sunlight reaching the trees in the sunny area - almost the same amount of sunlight reaching the trees in the shaded area - the amount of water available to the trees Hypothesis: Lichens produce their food from the sunlight with the help of its photosynthetic partner. It is more likely for lichens to grow on trees in large number in an area that has more sunlight compared to an area that is shaded. ...read more.

Middle

shaded area sx and sy represents the standard deviation of the two samples Calculations for the sunny area: Mean = x = ?x n Note: x - mean of the total number of squares covered by lichen in sunny area ?x - the total number of squares covered by lichen n - the number of samples x = 973 20 x = 48.65 Standard deviation = s�x = ?(x - x)� n - 1 Note: s�x - represents the standard deviation for the sunny area ?(x - x)� - represents the sum of the square of the difference between the number of squares filled by lichen and the mean of the squares filled n - the number of samples s�x = 20.24 Calculations for the shaded area: Mean = y = ?y n Note: y - mean of the total number of squares covered by lichen in shaded area ?y - the total number of squares covered by lichen n - the number of samples y = 314 20 y = 15.70 Standard deviation = s�y = ?(y - y)� n - 1 Note: s�y - represents the standard deviation for the shaded area ?(y - y)� - represents the sum of the square of the difference between the number of squares filled by lichen and the mean of the squares filled n - the number of samples s�y = 4.84 Difference between the mean of lichen cover in sunny and shaded area: Difference between the mean = [x - y] ...read more.

Conclusion

* The water content in the soil from where the trees grew could not be accurately known and so it was kept constant by just feeling the amount of moist in the soil, which is not very reliable. * The availability of sunlight cannot be exactly known and therefore after some observations, trees were chosen that had about the same amount of sunlight available. Improvements: * The ground from where a meter is measured should be flat, and if it is not a flat land, then clear out the area without damaging the environment or use another side of the tree. * An electronic equipment (i.e. an electric compass) should be used if available to find the exact point of direction looking for on the tree so as to control the variable as precisely as possible. * One should try and count the squares covered by lichen as accurately as possible so as to get the most reliable and precise answer as it is one of the most important points to be taken care of in this investigation. * The investigation would be better done and more exact answers would be obtained if other factors mentioned in the conclusion were also kept constant more accurately such as, the availability of water, temperature, side of the tree, humidity, altitude surface of the bark and the amount of sunlight available. * A repeat would defiantly give a more accurate and a reliable result especially for this experiment since counting the number of squares covered by lichen is the most important part and the whole conclusion is based on it. ...read more.

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