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# Measure the heart rate of Daphnia at different temperatures

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Introduction

Coursework Equipment * Compound microscope, light source, and lens tissues * Animal Cell and a spare cover slip * Petri Dish base * Paint Brush * Small beaker for collecting water * Supply of ice/warm water * Thermometer. * Basis electronic calculator * Pipette Aim To measure the heart rate of Daphnia at different temperatures Method Here is a method to show how I am going to conduct my experiment. Set up a microscope with a level stage. Half fill a petri dish base with tap water. Transfer Daphnia from its culture by using paint brush and place it in the special cover slip. The daphnia is placed in a tiny plastic ring, which is attached to the cover slip. Place another cover slip on top of the cell to retain the trapped animal, unharmed. Gently turn 'sandwich' over, holding it between finger and thumb, and then placing it under the surface of water of the petri dish. Place petri dish on stage of the microscope, examine using lowest magnification until heart is located, and change to highest magnification to see the heart in more detail. ...read more.

Middle

111 123 144 135 138 Daphnia 3 66 78 84 93 105 105 144 129 135 150 120 90 These results have been plotted onto a line graph. Hypothesis During this experiment I believe I will come across the following results. * The amount of heart beats at the different temperatures will not vary a lot. * The Daphnia's heart will stop once the temperature has exceeded 30 degrees Celsius. * Around 25 degrees Celsius would be the optimum temperature for which there would be the greatest number of heartbeats. * The 3 sets of Daphnia will have similar results. * The results will not be completely accurate because the heart rate count will be hard to record due to the how quick it will be beating and because the daphnia will not be in focus all of he time as it moves around a lot. Diagrams Water fleas are easy to find. Most ponds will provide enough of these small crustaceans. They are ideal subjects for study under the microscope. ...read more.

Conclusion

Moina withstand extremes even more, resisting daily variations of 5-31 deg C (41-88 F); their optimum being 24-31 deg C (75-88 F). From my results I found that the optimum temperature for the Daphnia is 40 after calculating the average of each temperature the Daphnia was exposed to. My hypothesis is that with an increase in temperature a Daphnia's heart rate will increase. The reason for this is that the chemical reactions that occur in the Daphnia are dependent on certain enzymes, or proteins to help them proceed. As the temperature of the water is increased, the metabolism of the Daphnia increases also; this is due to chemical reactions occurring faster at higher temperatures due to an increase in kinetic energy. As a consequence of this increase, the heart has to beat faster as more Carbon Dioxide is produced from the cells during respiration. This can cause acidic conditions which will eventually denature enzymes, so more oxygen needs to circulate which is why the heart speeds up. The results also show that with the decrease in temperature less cell respiration is occurring and so the heart beats at a slower pace. Kieron Harper ...read more.

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