AS & A Level Biology - 9700 Paper 5 2018 Winter Zone 1

Transpiration in plants can be investigated using a potometer, which measures water uptake by plants. Fig. 1.1 shows a potometer that was used by a student.

As water is lost by the leaves through transpiration, the air bubble moves along the graduated tube. The student used this apparatus to investigate the effect of light intensity on the rate of transpiration in plants.
(a) (i) State the independent variable and the dependent variable in this investigation.
independent ...........................................................................................................................
dependent ..............................................................................................................................
[2]
(ii) List three variables that should be controlled in this investigation and describe how the student could standardise two of these variables. ......................................................................................................................................
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[3]
(b) Describe how the student could set up and use the potometer shown in Fig. 1.1 to investigate the rate of transpiration at different light intensities.
Your method should be set out in a logical way and be detailed enough to let another person follow it.
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[6]
(c) The student carried out further experiments, using the same apparatus, to investigate the effect of two different environmental carbon dioxide concentrations on the rate of transpiration. These experiments were carried out at a high light intensity and at a low light intensity. The leafy shoots used in the experiments were taken from the same plant and each shoot had five leaves. The student calculated the percentage reduction in the transpiration rate from 50 ppm to 730 ppm of carbon dioxide at low light intensities. The results are shown in Table 1.1.
[Table_1]
ppm = parts per million
(i) Complete Table 1.1 by calculating the percentage reduction in transpiration rate from 50 ppm to 730 ppm of carbon dioxide at the high light intensity.
Show your working.
[2]
(ii) The student concluded that, as carbon dioxide concentration increased, the transpiration rate in plants decreased at all light intensities.
Explain why this conclusion may not be valid.
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[2]

Transpiration in plants can be investigated using a potometer, which measures water uptake by plants. Fig. 1.1 shows a potometer that was used by a student.

As water is lost by the leaves through transpiration, the air bubble moves along the graduated tube. The student used this apparatus to investigate the effect of light intensity on the rate of transpiration in plants.
(a) (i) State the independent variable and the dependent variable in this investigation.
independent ...........................................................................................................................
dependent ..............................................................................................................................
[2]
(ii) List three variables that should be controlled in this investigation and describe how the student could standardise two of these variables. ......................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
[3]
(b) Describe how the student could set up and use the potometer shown in Fig. 1.1 to investigate the rate of transpiration at different light intensities.
Your method should be set out in a logical way and be detailed enough to let another person follow it.
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[6]
(c) The student carried out further experiments, using the same apparatus, to investigate the effect of two different environmental carbon dioxide concentrations on the rate of transpiration. These experiments were carried out at a high light intensity and at a low light intensity. The leafy shoots used in the experiments were taken from the same plant and each shoot had five leaves. The student calculated the percentage reduction in the transpiration rate from 50 ppm to 730 ppm of carbon dioxide at low light intensities. The results are shown in Table 1.1.
[Table_1]
ppm = parts per million
(i) Complete Table 1.1 by calculating the percentage reduction in transpiration rate from 50 ppm to 730 ppm of carbon dioxide at the high light intensity.
Show your working.
[2]
(ii) The student concluded that, as carbon dioxide concentration increased, the transpiration rate in plants decreased at all light intensities.
Explain why this conclusion may not be valid.
..................................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
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[2]

(a) (i) Suggest two variables that need to be standardised when using the disc diffusion method in this study.

1 .......................................................................................................................................................
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2 .......................................................................................................................................................
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(ii) Describe how you would determine the sensitivity of $E. coli$ to each antibiotic.

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(b) Table 2.1 shows the results of this investigation.

[Table_1]

(i) Comment on the standard deviations for antibiotic use as shown in Table 2.1.

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(ii) Suggest two reasons why the number of prescriptions issued for antibiotics may not give an accurate measure of antibiotic use by patients.

1 .......................................................................................................................................................
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2 .......................................................................................................................................................
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(c) The number of prescriptions issued for antibiotics varied considerably between clinics.
The researchers wanted to find out whether there was a correlation between the number of prescriptions for each of the five antibiotics issued by a clinic and the percentage of urine samples containing resistant $E. coli$.
Spearman's rank correlation test was used for this analysis.
The results of this analysis are shown in Table 2.2.

[Table_2]

Table 2.3 shows the critical values for $r_s$ at five levels of significance for the data collected in this study.

[Table_3]

(i) Suggest why the Spearman's rank correlation test was used in this study.

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(ii) State a null hypothesis for the Spearman's rank correlation test for this study.

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(iii) Using Table 2.2 and Table 2.3, identify which antibiotics showed a statistically significant correlation between the number of prescriptions and the presence of resistant strains of $E. coli$ in urine samples. Give a reason for your answer.

antibiotics .......................................................................................................................................................
reason ..........................................................................................................................................................
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(d) The percentage of patients with ampicillin-resistant $E. coli$ infections varies with age and gender, as shown in Fig. 2.2.



Describe and explain the trends shown by these data.

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.......................................................................................................................................................... [3]

(a) (i) Suggest two variables that need to be standardised when using the disc diffusion method in this study.

1 .......................................................................................................................................................
..........................................................................................................................................................
2 .......................................................................................................................................................
.......................................................................................................................................................... [2]

(ii) Describe how you would determine the sensitivity of $E. coli$ to each antibiotic.

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.......................................................................................................................................................... [2]

(b) Table 2.1 shows the results of this investigation.

[Table_1]

(i) Comment on the standard deviations for antibiotic use as shown in Table 2.1.

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.......................................................................................................................................................... [2]

(ii) Suggest two reasons why the number of prescriptions issued for antibiotics may not give an accurate measure of antibiotic use by patients.

1 .......................................................................................................................................................
..........................................................................................................................................................
2 .......................................................................................................................................................
.......................................................................................................................................................... [2]

(c) The number of prescriptions issued for antibiotics varied considerably between clinics.
The researchers wanted to find out whether there was a correlation between the number of prescriptions for each of the five antibiotics issued by a clinic and the percentage of urine samples containing resistant $E. coli$.
Spearman's rank correlation test was used for this analysis.
The results of this analysis are shown in Table 2.2.

[Table_2]

Table 2.3 shows the critical values for $r_s$ at five levels of significance for the data collected in this study.

[Table_3]

(i) Suggest why the Spearman's rank correlation test was used in this study.

.......................................................................................................................................................... [1]

(ii) State a null hypothesis for the Spearman's rank correlation test for this study.

.......................................................................................................................................................... [1]

(iii) Using Table 2.2 and Table 2.3, identify which antibiotics showed a statistically significant correlation between the number of prescriptions and the presence of resistant strains of $E. coli$ in urine samples. Give a reason for your answer.

antibiotics .......................................................................................................................................................
reason ..........................................................................................................................................................
..........................................................................................................................................................
.......................................................................................................................................................... [2]

(d) The percentage of patients with ampicillin-resistant $E. coli$ infections varies with age and gender, as shown in Fig. 2.2.



Describe and explain the trends shown by these data.

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.......................................................................................................................................................... [3]