he Effect of Gas Exchange on a Locusts' Breathing

The Effect of Gas Exchange on a Locusts' Breathing

Aim- To see the effect of Carbon dioxide on a locusts' ventilation

rate.

Method- Since the locust was already in the 20cm³ plastic syringe held

in a clamp, our first step was to monitor its ventilation movements.

By looking at the abdomen, we could clearly see the ventilation

movements of the locust, which we counted for thirty seconds. We

repeated this three times under normal atmospheric conditions.

Our next task was to count the breathing rate again, yet this time

under a Carbon dioxide enhanced environment. We took a three way tap

and attached this to the end of the plastic syringe, also we removed

the piston and fitted loosely a small amount of cotton wool. In order

for the atmosphere surrounding the locust to have a higher Carbon

dioxide level, we attached a straw to the end of the tap, turning it

to an open position and breathed into it for approximately fifteen

seconds. We removed the straw and turned the three way tap back to a

closed position to stop the atmosphere changing. Once this was done,

we counted once more the ventilation rate of the locust for thirty

seconds, repeating three times.

Once we had gathered the results, we removed the three way tap and the

cotton wool, however we did not replace the piston. Instead, we

positioned our thumb where the piston should have been, resting over

the top of the plastic syringe so that the locust could not escape. We

then moved the syringe around the room for approximately two minutes

to allow the atmosphere to return to normal. Returning the piston back

to its position carefully so the locust did not get harmed, we then

counted the ventilation rate of the locust, again for a time of thirty

seconds for three successive periods.

Results-

Normal Atmosphere (no. of ventilation movements/30 sec)

+ Carbon dioxide

(no. of ventilation movements/ 30 sec)

Normal Atmosphere (no. of ventilation movements/30 sec)

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