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Cambridge International Examinations

Cambridge International Advanced Subsidiary and Advanced Level
* 8 6 3 7 3 8 0 1 8 0 *

BIOLOGY 9700/53
Paper 5 Planning, Analysis and Evaluation May/June 2018
1 hour 15 minutes
Candidates answer on the Question Paper.
No Additional Materials are required.

READ THESE INSTRUCTIONS FIRST

Write your Centre number, candidate number and name on all the work you hand in.
Write in dark blue or black pen.
You may use an HB pencil for any diagrams or graphs.
Do not use staples, paper clips, glue or correction fluid.
DO NOT WRITE IN ANY BARCODES.

Answer all questions.

Electronic calculators may be used.

You may lose marks if you do not show your working or if you do not use appropriate units.

At the end of the examination, fasten all your work securely together.
The number of marks is given in brackets [ ] at the end of each question or part question.

This document consists of 11 printed pages and 1 blank page.

DC (SR/JG) 147460/3
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1 Sodium hydrogencarbonate indicator solution contains sodium hydrogencarbonate.

Some students found out on the internet that this indicator solution changes colour with pH.
The students also discovered that this indicator is used to determine the concentration of carbon
dioxide in a solution.

The students decided to use this indicator to measure the rate of photosynthesis in algal balls.
Algal balls are unicellular algae that are immobilised in alginate.
The students assumed that the rate of carbon dioxide uptake was proportional to the rate of
photosynthesis.

Fig. 1.1 shows the apparatus that the students used.

glass container

lamp indicator

algal balls

25 cm ruler

Fig. 1.1

A laboratory technician prepared a series of test-tubes containing hydrogencarbonate indicator

solution from pH 7.6 to pH 9.2. The colour of the indicator solution in each test-tube is described
in Table 1.1.

Table 1.1

increasing CO2 decreasing CO2

in indicator solution in indicator solution
pH 7.6 pH 7.7 pH 8.0 pH 8.2 pH 8.4 pH 8.6 pH 8.8 pH 9.0 pH 9.2
light dark light dark red light dark light dark
yellow yellow orange orange magenta magenta purple purple

(a) Suggest what was added to each of the test-tubes to maintain the pH.

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

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(b) Unicellular algae can be immobilised using a technique that is similar to that used to
immobilise enzymes.

Outline the method that the students would have used to immobilise the algae.

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(c) The students used the apparatus shown in Fig. 1.1 and the colours described in Table 1.1 to
investigate the effect of light intensity on the rate of photosynthesis.

The students proposed the following hypothesis:

As light intensity increases the rate of photosynthesis increases.

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

independent variable .........................................................................................................

dependent variable ............................................................................................................

[2]

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(ii) Describe a method the students could use to collect the data needed to test their
hypothesis.

Your method should be set out in a logical way and be detailed enough to let another
person follow it.

You should not repeat any details from (b) about how to prepare immobilised algal balls.

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(iii) The students were concerned that the lamp may have increased the temperature of the
solution in the container. Suggest how they could have attempted to control this variable.

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(d) The light intensity (I ) can be calculated using the formula shown in Fig. 1.2.

1
I=
distance 2
Fig. 1.2

Use the formula in Fig. 1.2 to calculate the light intensity for the experiment shown in Fig. 1.1.

I = .......................................................... [1]

The students decided that using a pH probe would give them more accurate data. They
decided to measure the pH change for one value of light intensity.

Fig. 1.3 shows their results.

9.3
9.2
9.1
9.0
8.9
pH 8.8
8.7
8.6
8.5
8.4
8.3
0 1 2 3 4 5 6 7 8 9 10
time / min

Fig. 1.3

(e) (i) State why the use of a pH probe provides more accurate data.

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(ii) The data shown in Fig. 1.3 were for a high light intensity.

On Fig. 1.3, sketch the curve that you would expect for a low light intensity. [1]

(iii) State why carbon dioxide is not a limiting factor in this investigation.

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(f) Certain weed killers work by reducing the rate of photosynthesis.

The students modified their method to investigate the effect of three different weed killers on
algae at the same light intensity.

The investigation was replicated a number of times and the pH was recorded after 30 minutes.
The students calculated the mean pH for each treatment, as shown in Table 1.2.

The students carried out t-tests to compare the mean pH for each of the treatments that used
weed killers with the treatment that used no weed killer (treatment 1).
The students calculated the value of t for each of the tests.

Table 1.2 shows the results from their investigation.

Table 1.2

mean pH
treatment contents after 30 p value
minutes
1 algal balls, indicator and distilled water 9.2
2 algal balls, indicator and weed killer A 8.5 < 0.001
3 algal balls, indicator and weed killer B 9.0 > 0.05
4 algal balls, indicator and weed killer C 8.7 < 0.05

(i) Suggest a null hypothesis for comparing the effect of treatment 2 with treatment 1.

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(ii) The t-tests were used to compare the means.

State one feature of data that allows use of the t-test.

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(iii) When calculating the effect of weed killer A on the rate of photosynthesis, 15 degrees of
freedom was chosen. The students carried out 7 replicates of treatment 1.

State how many replicates were carried out for treatment 2.

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(iv) The students concluded that the weed killers had a significant effect on the rate of
photosynthesis.

Explain to what extent the p values in Table 1.2 support their conclusion.

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[Total: 22]

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2 Lionfish are a type of fish native to the tropical waters of the Indian Ocean and Pacific Ocean.

Lionfish were first reported off the south east coast of the USA in the 1980s. Lionfish are an
alien species to this area. Their lack of a natural predator in these waters resulted in their
numbers increasing dramatically, allowing them to migrate to new areas. They have now become
established across the Caribbean. Their numbers are so high that they are now a threat to many
native species.

(a) In one year it was estimated that 5 million prey were consumed by 1000 lionfish.

Express these data as a ratio.

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

(b) Surveys to assess the changes in lionfish abundance have been carried out every year
since 2004. Divers have carried out visual transects at nine sites along a 15 km stretch of
continuous reef off the coast of one island in the Caribbean.

Visual transects involve swimming in a fixed direction across the reef for a set distance and
counting the number of lionfish.

(i) State one variable which was standardised in these surveys.

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The mean abundance of lionfish on the reef was calculated for each year. These values are
shown in Fig. 2.1 using a log scale. The bars show 95% confidence intervals.

2.5

2.0

1.5
mean abundance
of lionfish (log scale)
1.0

0.5

0.0

2004 2005 2006 2007 2008 2009 2010

year

Fig. 2.1

(ii) A group of students read an article stating that local people were being encouraged to
catch and eat lionfish in an attempt to reduce their numbers.

The students concluded that local people started catching and eating lionfish in 2008.

Explain to what extent the data in Fig. 2.1 supports their conclusion.

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(c) Some local communities hold annual fishing trips where they are encouraged to catch as
many lionfish as possible.

In 2010 and 2011, 16 boats took part in these fishing trips. The mean number of lionfish per
boat and the 95% confidence intervals were calculated.

Fig. 2.2 shows the results.

300

250

200
mean number of lionfish
caught per boat 150

100

50

0
2010 2011
year of catch

Fig. 2.2

The 95% confidence intervals are calculated from 2 × SM .

Standard deviation can be calculated by rearranging the equation for standard error shown
in Fig. 2.3.

s
SM =
n

where S M = standard error

s = standard deviation

n = number of boats

Fig. 2.3

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Use the data in Fig. 2.2 and the equation in Fig. 2.3 to calculate the standard deviation of the
mean number of lionfish caught per boat in 2010.

standard deviation for 2010 = .......................................................... [3]

[Total: 8]

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