An Investigation to Show the Effect of Temperature on Daphnia
Plan:
I will submerge some daphnia contained in a test tube in water of differing temperatures and measure their subsequent heart rates.
Hypothesis
I think that the heart rate of the daphnia will increase up until around 40ËšC at which point most of the daphnia's enzymes will have denatured and rate of metabolism will have stopped or decreased sufficiently to have stopped the daphnia's heart rate.
Apparatus list
Test tube
Beaker
Different temperatures of water
Daphnia
Pipette
Stop clock
Microscope
Slide
Safety
Follow usual lab safety rules. There are no major safety considerations in this experiment as the daphnia aren't harmful and water above 40ËšC will not be used.
Method
To determine if temperature does have an effect on the daphnia, I intend to carry out the following experiment. The experiment will involve measuring the cardiac activity of the daphnia at different temperatures, ranging from very cold (approx. 5 degrees Celsius) to quite warm (approx. 40 degrees Celsius).
· A selection of similar sized/age Daphnia will be taken.
· A variety of different temperatures of water will be set up, these temperatures will be kept constant whilst the daphnia are submersed in them. The temperatures will be set up by using ice to cool tap water down to lower temperatures and boiling water to heat it up. The temperature will be measured to within 0.1°C on a mercury thermometer to ensure accuracy. The temperatures will range from 10°C to approximately 40°C and it will be done at 5°C intervals.
· The daphnia will be submersed in the water and left to equilibrate for 3 minutes, after this time one of the Daphnia will be removed and put onto a microscope slide, this will then be quickly put under the microscope. -1-
· Under the microscope, the Daphnia will be observed for 20 seconds, this heart rate will be counted and recorded, this can the be multiplied by 3 to give a beats per minute. This way, the beats counted will be at as close temperature as possible, as they won't have time to cool / warm significantly.
· The experiment will be repeated twice for each temperature.
Dependant variable:
It is important to ensure that all variables are kept constant, allowing the experiment to be a fair one, to do this the following precautions should be taken:
· The Daphnia used should be of a similar size and age to ensure that they react in the same way to the different temperatures.
· The heartbeat should be counted as soon as possible after the
Daphnia is placed under the microscope to ensure that the temperature it has equilibrated to remains as close as possible and is not affected by the light source of the microscope.
· All of the Daphnia should be allowed the same amount of time to equilibrate to the temperatures, thus they all experience the same conditions and this makes the experiment more accurate.
· The same person should always count the heartbeats to ensure that judgement errors do not affect the overall results.
· Each daphnia should have the same transfer time from water to microscope. (If time exceeds 15 seconds, void that part of experiment and repeat.)
· The temperature of the water needs to be monitored constantly to ensure that the results are being recorded at consistent temperatures.
Independent variable
· The temperature of the daphnia will be changed from 10˚C to 40˚C with 5˚C increments. This will be done by allowing the daphnia to acclimatise to different temperatures by putting their container in different temperatures of water. The results for experiment will each be repeated three times.
· The heart rate of the daphnia will be counted by looking at them under a microscope with 100x magnification and taking heart beat for
20 seconds and multiplying this figure by 3 to give beats per