No questions found
(a) (i) State the independent variable being investigated. ....................................................................................................... [1]
(a) (ii) Outline the procedures the student could use to obtain these results. ........................................................................................................ ........................................................................................................ ........................................................................................................ ........................................................................................................ ........................................................................................................ ........................................................................................................ ........................................................................................................ ........................................................................................................ ........................................................................................................ [8]
(b) (i) Complete the calculation to find the value of $t$ for the internode length. Show your working. $$t = \frac{|\bar{x}_1 - \bar{x}_2|}{\sqrt{\frac{s_1^2}{n_1} + \frac{s_2^2}{n_2}}}$$ $$t = \frac{\sqrt{\frac{42}{30} + }} = 0.9$$ $t = ..........................................$ [3]
(b) (ii) State how the number of degrees of freedom was calculated. ........................................................................................................ ........................................................................................................ [1]
(b) (iii) State and explain the meaning of these results. ........................................................................................................ ........................................................................................................ ........................................................................................................ [2]
(c) (i) Explain how the actual thickness of the leaf could be measured. ........................................................................................................ ........................................................................................................ ........................................................................................................ [2]
(c) (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. ........................................................................................................ ........................................................................................................ ........................................................................................................ ........................................................................................................ ........................................................................................................ [3]
559
510
504
Fig. 2.1 shows a freshwater crustacean. This animal has a two-chambered heart that can be seen through the exoskeleton.
An investigation into the effect of temperature on heart rate was carried out using this organism to test the hypothesis:
Five crustaceans, each measuring 5mm in length, were placed in water of different temperatures and left for five minutes. The heart beat was counted for 20 seconds using a tally counter and stop watch. Table 2.1 shows the results of the investigation.
[Table_1]
(a) (i) Identify two variables that have been controlled during this investigation.
1. ..............................................................................................................
2. .............................................................................................................. [2]
(ii) Suggest one other variable that should be controlled.
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.............................................................................................................. [1]
(iii) Suggest one feature of the procedure which may cause the results to be inaccurate.
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.............................................................................................................. [1]
(iv) Suggest a reason why the student used five specimens at each temperature.
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.............................................................................................................. [1]
The student calculated the percentage change in heart rate for each specimen. Table 2.2 shows these results.
[Table_2]
(b) (i) Suggest why the student converted the raw data to percentage change.
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.............................................................................................................. [1]
(ii) Describe how the percentage change between 25\(^{\circ}\)C and 30\(^{\circ}\)C was calculated.
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.............................................................................................................. [1]
(iii) Predict the effect on the heart rate of an increase in temperature to 40\(^{\circ}\)C.
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.............................................................................................................. [1]
(c) Assess how far the results of the investigation support the hypothesis.
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.............................................................................................................. [2]
533
545
593
