AS & A Level Biology - 9700 Paper 5 2010 Winter Zone 2

(a) (i) State the independent variable being investigated.
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(ii) Outline the procedures the student could use to obtain these results.
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(b) (i) Complete the calculation to find the value of $t$ for the internode length.
Show your working.

$t = \frac{|\bar{x}_1 - \bar{x}_2|}{\sqrt{\frac{s_1^2}{n_1} + \frac{s_2^2}{n_2}}}$

$t = \frac{|\bar{x}_1 - \bar{x}_2|}{\sqrt{\frac{42}{30} + \frac{}{}}}$

$t = .........................................................$[3]

(ii) State how the number of degrees of freedom was calculated.
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(iii) State and explain the meaning of these results.
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(c) (i) Explain how the actual thickness of the leaf could be measured.
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(ii) With reference to the student’s results, state what conclusions can be drawn about the differences in adaptations shown by shaded leaves and exposed leaves of the plant.
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(a) (i) Identify two variables that have been controlled during this investigation.
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(ii) Suggest one other variable that should be controlled.
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(iii) Suggest one feature of the procedure which may cause the results to be inaccurate.
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(iv) Suggest a reason why the student used five specimens at each temperature.
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(b) (i) Suggest why the student converted the raw data to percentage change.
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(ii) Describe how the percentage change between 25 °C and 30 °C was calculated.
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(iii) Predict the effect on the heart rate of an increase in temperature to 40 °C.
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(c) Assess how far the results of the investigation support the hypothesis.
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