Assignment: Measuring the rate of respiration of living organisms
Apparatus used:
Tap - when both are closed,
Abany change in gas volumes
between the2 chambers will
cause the manometer fluid to
move
Airtight bung
Chamber housing
Organism
Control chamber
Gauze
Manometer fluid
Weighed soda
Lime why
Weighed soda lime (equal
mass to soda lime in other
chamber + mass of organism)
Below is a table of results from an experiment in which the temperature of the environment around
an organism was varied. In each case the number of units of oxygen used was measured for a set
time by recording how far the manometer fluid moved to the left.
Temperature oC
0
10
20
30
40
50
Number of units of O2 used in a set time
Mouse
Large grasshopper
30
0
25
2
18
4
15
8
25
16
35
20
(1) Use your knowledge of enzymes (gained last week?) to explain the respiration changes
of the grasshopper. (5 marks)
(2) Why is the pattern differrent in a mouse? (1mark)
(3) The mouse was 5 times heavier than the grasshopper, but the time for which respiration
was measured was 10 times longer for the grasshopper. How would these two facts
affect the results? (2 marks)
(4) Why is the respiration rate of the mouse higher than that of the grasshopper? (2 marks)