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)