Investigating Respiration Flashcards
how can you calculate the rate of respiration of an organism
by measuring the amount of oxygen consumed by organisms in a given time
what does the core practical, which uses woodlice, a water bath and a piece of equipment called a respirometer allow you to measure
it allows you to measure the effect of temperature on the rate of respiration of the woodlice
what other organisms could you use other than woodlice and why would they work
- you could use germinating seeds or beans
- because the seeds need to respire to provide energy for growth
explain the method carried out in the core practical
- some soda lime granules are added to two test tubes
- a ball of cotton wool is placed above the soda lime in each tube
- glass beads with the same mass as the woodlice are used in the control tube
- respirometer is set up with a syringe attached
- apparatus is left for a set period of time in a water bath set at 15C
- after time is over, you can repeat the experiment with the same time intervals at different temperatures
why are soda lime granules added to the test tubes
because the soda lime absorbs the CO2 produced by the respiring woodlice in the experiment
what safety precaution should you take when handling the soda lime and why
- you should wear safety goggles and gloves when handling it to protect the eyes and skin
- because soda lime is corrosive
why is the cotton wool placed above the soda lime for the woodlice to be placed in
- so that the woodlice dont come into contact with the soda lime
- as it is corrosive and would hurt them
what is the syringe set up in the respirometer used for
it is used to set the fluid in the manometer to a known level
what happens in the tube with the woodlice as the experiment is taking place
- there will be a decrease in the volume of air in the test tube with the woodlice
- this is because the woodlice are using up oxygen in the test tube as they respire
why does the liquid move to the test tube with the woodlice in it
- the respiring woodlice decrease volume of air in tube
- decrease in volume reduces the pressure in the tube
- causing the coloured liquid in the manometer to move towards the test tube containing wood lice
even though the woodlice are respiring, they produce carbon dioxide as a waste product which should keep the air pressure constant. why does the air pressure drop non the less?
because the CO2 they produce is absorbed by the soda lime so the CO2 doesnt affect the experiment
what is measured in the experiment
the distance moved by the liquid in a given time
what can the distance moved by the liquid in a given time be used to calculate and what does it give you
- the volume of oxygen taken in by the woodlice per minute
- this gives you the rate of respiration (cm^3 min^-1)
if the temperature of the water in the water bath is increased and the same time interval is used, what would happen to the rate of respiration
the rate of respiration increases
what ethical precaution should be taken when carrying out this experiment with woodlice
you shouldnt leave the woodlice in the respirometer for too long, or they may run out of oxygen and die
