AS & A Level Biology - 9700 Paper 5 2009 Summer Zone 1

(a) Fig. 1.1 shows a simple apparatus that can be used to identify the tissue that conducts water up a stem. A cut shoot was placed in dye solution.
After several hours the dye accumulated in the leaves.
[Image_1: Simple Apparatus with Leafy Shoot, Oil, Dye Solution]

(i) The stem was further investigated to locate the tissue that conducts water.
Describe a method by which the tissue through which water is conducted in the stem can be identified.
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(ii) Explain why a cut shoot is used rather than an intact plant with roots.
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(b) (i) Describe how this apparatus could be set up and used to find the rate of movement of water up the stem.
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(ii) State how the rate of water movement is calculated.
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(iii) Predict the effect on the rate of water movement of adding a respiratory inhibitor to the dye solution.
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(a) A species of snail is found in a variety of habitats. The shells of these snails may have dark bands on the surface of the shell (banded) or may not have any bands on the shell (unbanded). These shells are shown in Fig. 2.1.



These snails are eaten by birds. The birds break the shell of the snail on a stone and eat the soft body. The shell remains are left by the stones.

In an investigation all the snails were removed from two areas where trees were growing. One area had birds that feed on this snail, the other area did not. An equal number of banded and unbanded snails were released into both areas.

- In the area with the predatory birds the types of broken snail shells found around the stones were counted over a two week period.

- In the area without predatory birds the same number of living snails was collected and the number of banded and unbanded snails counted after two weeks.

Table 2.1 shows the results of this investigation.

[Table_1]

(i) Identify the independent variable and the dependent variable in this investigation.

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(ii) Suggest an explanation for the results of this investigation.

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(b) In another investigation in a different area, the population of this snail was investigated using a capture/recapture method.

A sample of the snail population was collected and marked. These snails were then released and at a later time another sample was collected and the number of marked individuals counted.

The population was estimated using the formula:

$$\text{number of animals marked in the first sample} \times \text{total number of animals in the second sample}$$
$$\text{number of marked animals in the second sample}$$

Table 2.2 shows the results of two different investigations of the same population.

- In investigation 1, the second sample was collected 24 hours after release.

- In investigation 2, the second sample was collected 72 hours after release.

[Table_2]

(i) Complete Table 2.2 by calculating the total population estimated from investigation 1.

Write your answer in Table 2.2.[1]

(ii) Suggest why the procedure used to estimate the population means that the estimate made from investigation 1 is more likely to be reliable than the estimate from investigation 2.

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(a) (i) Suggest why a continuous culture system was used to test the growth rate of this yeast.
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(ii) Identify two variables that should be controlled during the fermentation.
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(b) (i) Explain how the mean values in Table 3.1 were obtained.
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(ii) State what the standard deviations tell you about these results.
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(iii) State whether or not the data in Table 3.1 indicate that the difference in growth rate of $R. \textit{glutinis}$ at pH 5.2 is significantly different from the growth rate at pH 4.0.
Give a reason for your answer.
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(iv) A $t$-test was carried out on the results for pH 4.0 and pH 5.2 and gave the value, $t = 2.4$
State the number of degrees of freedom for this $t$-test.
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(c) Based on the findings of the $t$-test, a student concluded that pH 5.2 was optimum for the production of the enzyme $\alpha$-arabinofuranosidase by $R. \textit{glutinis}$. Suggest two reasons why this conclusion may not be valid.
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