Name: _______________________________________________ 	

  	
  	
Topic 1 Lifestyle, Health & Risk	

 	
Date:	

  	
  	
Time: 27 minutes	
  	
Total marks available: 27	
  	
Total marks achieved: ______ 	

  	

  	

  	

  	

  	

  	

  	
Practical skill focus 	

	

Questions

Q1.  A student investigated the effect of temperature on the heart rate of Daphnia.

(a)  Use the lines A to B to calculate the actual length of this Daphnia.									(2)

Answer ...........................................................

(b)  The student used five Daphnia in the investigation.
The Daphnia's heartbeats were counted over a 20-second period.
A stopwatch was used and a pencil mark made on a piece of paper while observing the Daphnia through a low powered microscope.
The number of heartbeats was counted three times for each Daphnia.
This was repeated at five different temperatures using the same Daphnia each time.
This was then repeated using the four other Daphnia.
The results obtained are shown in the table below.

(i)  Explain why the number of heartbeats was measured in 20 seconds rather than in one minute.
(2)
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(ii)  The mean heart rate at 5 °C is 20.2 beats in 20 seconds. Calculate how many times faster the mean heart rate is at 25 °C than at 5°C.
(2)

Answer ...........................................................

(iii)  The student concluded that temperature increased the heart rate of Daphnia.
Analyse the data to explain how this investigation could be modified to improve the validity of this conclusion.
(3)
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(c)  Discuss the ethical issues that might arise from the use of invertebrates in investigations.
(4)
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(Total for question = 13 marks)

Q2.    The effect of salt in the diet on blood pressure was investigated.
This investigation involved 15 males and 5 females, all between 20 and 30 years old. They were split into two groups, A and B, each of 10 people.
Group A had a diet containing 3 g of salt per day. Group B had a diet containing 9 g of salt per day.
The systolic blood pressures, measured in mmHg, were recorded during one year.
The results are shown in the graph.

Explain how the validity of this investigation could be improved.
(3)
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(Total for question = 3 marks)
 Q3.  Fruit juices contain various concentrations of vitamin C.
The graph shows the vitamin C concentration of five fruit juices.

Devise an investigation that can be used to collect these data.
(5)
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 (Total for question = 5 marks)
 
Q4.   There are many products that may increase the ability of sperm to swim. One of these products contains zinc sulphate.
Devise an investigation to obtain valid data to show whether taking zinc sulphate tablets affects the ability of sperm to swim.
(6)
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  (Total for question = 6 marks)

Q1.
No Examiner's Report available for this question

Q2.
 
This question asked candidates to explain how the validity of the investigation, described at the start of the question, could be improved.
It was pleasing to see a large number of candidates referred back to the details of the investigation and recognised that the number of males and females were uneven and that there was a small sample size. These were the most commonly awarded marks.
As the question had specifically stated 'this' investigation, improvements relating to different investigations that could be carried out were not credit worthy. A significant minority of candidates did explain suitable improvements that would improve the validity of the investigation.
Approximately 10% of candidates gained full marks on this question.

Results Plus: Examiner Comments
This response gained the most commonly awarded marking points; the equal numbers of males and females and the larger sample size. 

Increasing the variation of salt diets was not relevant.

Results Plus: Examiner Comments
This response gained full marks for a clear explanation of how the validity of this investigation could be improved.

 

Q3.
 
The question required candidates to devise an investigation that could be used to collect the data that was shown in the graph. Candidates therefore needed to apply their knowledge of the core practical to this context.
It was clear from their responses that some candidates had not done this core practical.
The majority of candidates understood how to do a titration with DCPIP and were able to give this method to gain marking point 1 and 4. There were two possible methods for a titration with DCPIP. The method where the juice was poured into the burette was seen more commonly than the one where DCPIP was in the burette. This impacted on marking points 2 and 4.
However, some candidates described methods involving using a pipette to add drops of juice / DCPIP which was not credit worthy for mark point 1.
A significant minority of candidates referred to controlling the volume of juice, but could not be awarded mark point 2 as the volume of juice was their dependent variable in the method they gave. In this scenario, the idea of DCPIP decolourising could not be awarded.
When mark point 3 was awarded, it was usually for controlling the concentration of DCPIP or the age of the fruit juice.
Marking points 5 and 6 were very rarely awarded as candidates did not refer back to the graph and therefore did not explain how the concentration of vitamin C could be determined. Only 5% of candidates gained one or more of these marking points.

Results Plus: Examiner Comments
This response gained three marks for a titration with a controlled volume of DCPIP which has a suitable end point. 

The candidate has not controlled another variable or related the method to the data in the graph so mark points 3, 5 and 6 could not be awarded.

Results Plus: Examiner Tip
Make sure you describe variables which need to be controlled to ensure a valid investigation.

Results Plus: Examiner Comments
This response correctly describes an investigation that could be used to collect the data shown in the graph. 

There is a titration with a known volume and concentration of DCPIP. The volume of juice needed to decolourise DCPIP is being measured and then compared to a standard solution of vitamin C. 

Full marks were awarded.

 

Q4.
No Examiner's Report available for this question

Mark Scheme

Q1.

Q2.

 

Q3.

 

Q4.