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Investigating the effect of caffeine on the heart rate of Daphnia

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Core Practical Write Up Testing the tensile strength of celery xylem and vascular bundles Planning I am going to be testing the tensile strength of celery's vascular tissue with and without sclerenchyma and comparing it to see how the sclerenchyma affects the overall strength of the vascular tissues. Dependant variable: The dependant variable in this experiment is the mass/force needed to snap the vascular tissue strands. This will be measured by slowly placing masses on the end of the tissues until the strand snaps. We will then count up the mass added to the vascular tissues. Independent variable: The independent variable is whether or not the vascular bundle will include sclerenchyma or not. 3 groups are going to be testing without the sclerenchyma and 4 groups are going to be testing with the sclerenchyma. Controlled variables: We are going to be controlling the length of vascular tissue used which will be kept at 15cm throughout the class. The batch of celery used is also going to be controlled as much as we can use the celery from the same bunch each time. ...read more.


With sclerenchyma 500 Without sclerenchyma 80 After having an estimate to the masses we should for the experiment we carried it out, in my group with I used 10g masses for vascular tissues not containing sclerenchyma. Here are my own results: Test 1 Test 2 Test 3 Test 4 Test 5 Average 90g 150g 140g 80g 180g 128g The range for my result was (180-80) 100. Here are the class results for groups with and without sclerenchyma. Mass needed to break the vascular bundles (g) Average (g) Vascular bundles with sclerenchyma 577 600 397 153 525 Vascular bundles without the sclerenchyma 145 140 128 - 138 The result highlighted is an anomalous result and has not been included in the average. The next table shows the same results converted into the amount of force needed to break the vascular bundles. Force needed to break the vascular bundles (N) Average (N) Vascular bundles with sclerenchyma 5.77 6.00 3.97 1.53 5.25 Vascular bundles without the sclerenchyma 1.45 1.40 1.28 - 1.38 I have also drawn out bar graphs containing error bars and averages attached. Conclusion From my results I can see there is a definite increase in force and mass needed to break the vascular bundles attached to the sclerenchyma. ...read more.


We did not have time to improve our methods or carry out repeats. The results were validated by the whole class although there may have been some variations in the range most of the results were still following the same pattern and trends shown and expected in the hypothesis. This experiment in my opinion was valid and reliable in proving my hypothesis correct. If I could extend or improve this experiment I think I would find a better method to holding the vascular tissue that took up less of the tissue, for example using just one bull dog clip and holding it up right. Maybe hanging weights off it this way would be a better idea. Making more repeats maybe 10 for each one would give a better average. If I was to extent this experiment I could try to test how the length of the plant affects the tensile strength of the overall vascular tissue and change my independent variable to length of plant tissue. Maybe still keep the variables from this experiment but extend my overall result and testing. More time would also be needed in consideration. ?? ?? ?? ?? Shivalee Patel ...read more.

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