This investigation will attempt to prove, whether or not a change in temperature will affect the respiration rate (and therefore the breathing rate) of a locust.

This investigation will attempt to prove, whether or not a change in temperature will affect the respiration rate (and therefore the breathing rate) of a locust. Locusts are 'poikilothermic' and I will be taking this factor into account when predicting the locust's reaction to a temperature change.

Preliminary Testing

Preliminary tests consisted of a 'mock experiment', a kind of trial run of the real thing. The test was carried out as follows:

· Fill a beaker with water of the desired temperature

· Place the locust in a boiling tube and place this in the water

· Observe the number of times the locust's abdomen moves up and down and record the breathing rate over a period of time

· Repeat for different temperatures

These 'basic' preliminary tests uncovered a few 'flaws' in the experiment and helped to highlight a few aspects that needed careful consideration. Aspects that will need to be altered are, the length of time left for the locust to acclimatise to the new temp. and the length of time left for the locust to recover. Other factors that will need consideration are, whether or not to take the locust out of the tube to monitor its breaths, and over how long should its breathing be monitored?

It was decided that the locust would need 3 minutes to acclimatise to the new temperature and that 4-5 minutes would be sufficient time for it to recover after being subjected to a change in temp. A period of acclimatisation is required because preliminary tests showed that locusts took an average of 3 minutes for their breathing rate to be affected by the temperature change. A period of recovery is required because it took an average of 4 minutes, 30 seconds to return their breathing rate to normal

Research into 'Locusts' showed they breathe through their tracheae, and a movement ...

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Research into 'Locusts' showed they breathe through their tracheae, and a movement of their abdomen draws air in and pushes it out. This means that, in order to count the number of breaths the locust takes, we can count the number of times its abdomen moves up or down. One breathe can be counted as when the abdomen goes up then comes back down.

Method

After considering all the factors mentioned above I devised the following experiment:

· Fill a beaker with 250 cm of water at the chosen temperature (eg. 10 C )

· Place a test-tube in the water being careful not to get the inside wet

· Allow a few minutes for the boiling-tube to reach the same temperature as the water in the beaker. This can be tested by holding a thermometer inside the boiling-tube (It is important that the boiling-tube is already at the desired temperature when the locust is inserted, so that no time is wasted while the boiling-tube warms up. This will ensure a fair test)

· When the tube is the same temperature as the water place a 'head rest' in the tube to keep the locust still when inserted

· Insert the locust and allow 3 minutes for it to 'acclimatise'(as already explained)

· Remove the tube (containing the locust) from the beaker and count the number of times the locust's abdomen moves up and down in 30 seconds.

· Place the locust in an empty beaker and allow 4 - 5 minutes recovery time before repeating the test or trying a new temperature to ensure that the locust is 'fresh' and stable to experience another temperature change

Hypothesis

Locusts are poikilothermic animals, which means that the environment they are in controls their body temperature. If they are in a warm environment then they become warm and so do their cells. This speeds up their metabolism (the chemical reactions taking place inside their body) including the rate at which they respire. The respiration rate increases because the locust's body requires more oxygen in order for it's metabolism to speed up. Therefore I predict that an increase in temperature will mean an increase in the respiration rate (breathing rate) of the locust.

Results

Mass Of Locust Temp. Of Water Breaths per 30 secs.(1) (2) (3) Average

Conclusion

From the results I can clearly see that, as the temperature rose, the breathing rate of the locust rose as well. This proved my hypothesis to be true as I predicted that this would happen due to the fact that locusts are poikilothermic. Therefore, a temp. increase speeds up the rate at which enzymes work and so speeds up the locust's metabolism. The rate of chemical reactions taking place inside the body of the locust increased and therefore the rate of respiration also increased.

Evaluation

Despite the preliminary testing and efforts to keep the test 'fair' there were some uncontrollable factors that would have made the results slightly inaccurate. The fact that we were dealing with live locusts meant that handling them was often a problem, and also the fact that each one would be different to the other. When dealing with living things it is difficult to take what happens as a 'normal' occurrence because one locust may behave differently to another. To try to limit this possible source of inaccuracy the test at each temperature was done 3 times, this would improve the accuracy of the results but it would still be a big assumption to say that this is what would happen to every locust. If this test was to be done again I would like to use 2 or 3 different locusts to use in the investigation. By doing this it would then be a more reliable conclusion to say that 'this happens for every locust'.

Other sources of inaccuracy may have come from, not allowing enough time for acclimatisation or recovery but due to the amount of time allocated for the investigation these times had to be limited. In future investigations these times could be longer and this would improve the accuracy of the results.

One final thought for a future experiment could be to investigate the different reactions of male and female locusts. It was not realised until after the experiment that we had been using a male and that his reactions may have been different to a female's. Despite these few inaccuracies the investigation was carried out fairly accurately and the results were successfully anticipated in the hypothesis due to investigations into locusts before beginning the experiments.