2: Respirometers

Question 1

Define ‘respirometer’.

Answer 1

any device that is used to measure respiration rates

Question 2

There are many designs of respirometer, but most involve these parts:

Answer 2

1. sealed glass or plastic container in which the organism or tissue is placed
2. an alkali, such as potassium hydroxide, which absorbs carbon dioxide produced by cell respiration. The volume of air inside the respirometer should therefore reduce as a result of oxygen being used in cell respiration by the organisms in the respirometer.
3. capillary tube containing fluid, connected to the container, which allows the volume of air inside the respirometer to be monitored.

Question 3

Which organisms are usually used in respirometer experiments?

Answer 3

• fly larvae

- other invertebrates

Question 4

When assessing ethical implications of a respirometer experiment, what should we ask?

Answer 4

1. will animal suffer pain/harm?
2. unacceptable risks for animal? e.g. contact with the alkali
3. will animals have to be removed from their natural habitat? if yes, can they be returned?
4. necessary to use animal? could another organism be used e.g. germinating seeds

= there are strict restrictions on using vertebrates in research

Question 5

State steps in analysing data from respirometer experiments.

Answer 5

1. Calculate mean results (if experiment includes repeats)
2. Plot graph with range bars (although graphs in science papers usually include error bars)
3. Describe the trend
4. Evaluate the data (range bars show variation between replicates, but if variation within test smaller than variation between tests, then results are probably significant)