No questions found
(a) Suggest what was added to each of the test-tubes to maintain the pH.
[Table_1]
...................................................................................................................................................................................... [1]
(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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...................................................................................................................................................................................... [3]
(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]
(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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........................................................................................................................................................................................ [5]
(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.
......................................................................................................................................................................................
...................................................................................................................................................................................... [1]
(d) The light intensity \( I \) can be calculated using the formula shown in Fig. 1.2.
\[ I = \frac{1}{\text{distance}^2} \]
Use the formula in Fig. 1.2 to calculate the light intensity for the experiment shown in Fig. 1.1.
I = ................................................................. [1]
(e) (i) State why the use of a pH probe provides more accurate data.
...................................................................................................................................................................................... [1]
(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.
......................................................................................................................................................................................
...................................................................................................................................................................................... [1]
(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_2]
(i) Suggest a null hypothesis for comparing the effect of treatment 2 with treatment 1.
......................................................................................................................................................................................
...................................................................................................................................................................................... [1]
(ii) The \( t \)-tests were used to compare the means.
State one feature of data that allows use of the \( t \)-test.
......................................................................................................................................................................................
...................................................................................................................................................................................... [1]
(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.
...................................................................................................................................................................................... [1]
(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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...................................................................................................................................................................................... [3]
599
517
500
(a) Suggest what was added to each of the test-tubes to maintain the pH.
[Table_1]
...................................................................................................................................................................................... [1]
(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.
......................................................................................................................................................................................
........................................................................................................................................................................................
........................................................................................................................................................................................
........................................................................................................................................................................................
........................................................................................................................................................................................
........................................................................................................................................................................................
........................................................................................................................................................................................
........................................................................................................................................................................................
........................................................................................................................................................................................
........................................................................................................................................................................................
...................................................................................................................................................................................... [3]
(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]
(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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........................................................................................................................................................................................ [5]
(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.
......................................................................................................................................................................................
...................................................................................................................................................................................... [1]
(d) The light intensity \( I \) can be calculated using the formula shown in Fig. 1.2.
\[ I = \frac{1}{\text{distance}^2} \]
Use the formula in Fig. 1.2 to calculate the light intensity for the experiment shown in Fig. 1.1.
I = ................................................................. [1]
(e) (i) State why the use of a pH probe provides more accurate data.
...................................................................................................................................................................................... [1]
(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.
......................................................................................................................................................................................
...................................................................................................................................................................................... [1]
(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_2]
(i) Suggest a null hypothesis for comparing the effect of treatment 2 with treatment 1.
......................................................................................................................................................................................
...................................................................................................................................................................................... [1]
(ii) The \( t \)-tests were used to compare the means.
State one feature of data that allows use of the \( t \)-test.
......................................................................................................................................................................................
...................................................................................................................................................................................... [1]
(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.
...................................................................................................................................................................................... [1]
(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.
......................................................................................................................................................................................
......................................................................................................................................................................................
......................................................................................................................................................................................
......................................................................................................................................................................................
...................................................................................................................................................................................... [3]
565
525
540
(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.
........................................................ [1]
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.
(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.
........................................................... [3]
(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.
The 95% confidence intervals are calculated from $2 \times S_M$.
Standard deviation can be calculated by rearranging the equation for standard error shown in Fig. 2.3.
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]
509
553
519
(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.
........................................................ [1]
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.
(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.
........................................................... [3]
(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.
The 95% confidence intervals are calculated from $2 \times S_M$.
Standard deviation can be calculated by rearranging the equation for standard error shown in Fig. 2.3.
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]
527
539
570
