Respiration (CIE IGCSE Biology: Co-ordinated Sciences (Double Award))

A woodlouse is a small animal.  

The rate of respiration of a woodlouse can be measured using a simple respirometer as shown in Fig. 1. 

As the woodlouse respires the drop of coloured liquid moves along the capillary tube.

Fig. 1

Record the position of the drop of coloured liquid in the capillary tube shown in Fig. 1 at the start and after 30 minutes.

Give your answer in mm.

[1]

Calculate the distance moved by the drop of coloured liquid in 30 minutes.

Give your answer in mm.

[1]

Calculate the rate of movement of the drop of coloured liquid in mm per minute. 

Give your answer in mm per minute and to one decimal place. 

[2]

The rate of movement of the drop of coloured liquid along the respirometer can be used to estimate the rate of respiration. 

A student used a respirometer to investigate the rate of respiration in four animal species.  

The results are shown in Table 1.

Table 1

Animal species	Rate of movement of the drop of coloured liquid / mm per minute
	Trial 1	Trial 2	Trial 3	Mean
A	1.5	1.7	1.3
B	0.9	1.0	0.7	0.9
C	2.4	2.6	2.5	2.5
D	1.9	2.0	1.9	1.9

Calculate the missing mean for animal species A. 

[1]

Plot a bar chart on the grid to show the mean rate of movement of the drop of coloured liquid in the capillary tube for the four animal species. 

[3]

State the letter of the animal species which has the highest rate of respiration.  

[1]

Suggest a suitable control for the investigation described in 1b). 

[1]

The student decided it would be better to calculate the rate of respiration per gram of animal so that the values could be compared.

Describe how the student could find out the rate of respiration per gram of animal.

[2]