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# The measurement of the daphnia's heart rate

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Introduction

The measurement of the daphnia's heart rate Daphnia is the name of a group of small, aquatic crustaceans commonly called 'water flies'. Because their exoskeletons are clear it is possible to watch daphnia hearts without cutting them open. This also allows the changes in daphnia heart rate to be studied quite easily. Hypothesis I predict that a daphnia should have a heartbeat of 190 to 200 per minute. However this would also be dependent of the room temperature as daphnias are cold blooded animals, they do not thermo regulate which means that their body temperature is the same as the water they are floating in. Daphnia is a group of small, aquatic crustaceans commonly called 'water flies'. Because their exoskeletons are clear it is possible to watch daphnia hearts without cutting them open. This also allows the changes in daphnia heart rate to be studied quite easily. Dependent Variables In this investigation, I will be measuring the heart rate of the water flea. I will do this by placing the water flea under a microscope and count its heartbeat. I will be able to do this because the water flea is translucent and I will be able to see its heart beating. I will do it for fifteen seconds, then multiply the result by four to get a minute worth. ...read more.

Middle

1 226-230 0 231-235 1 236-240 3 241-245 1 246-250 0 251-255 1 Table showing the calculation of plotting a histogram Frequency Group Class width Frequency Frequency Density 80-84 5 1 0.2 85-90 5 0 0 91-95 5 0 0 96-100 5 0 0 101-105 5 0 0 106-110 5 0 0 111-115 5 0 0 116-120 5 0 0 121-125 5 1 0.2 126-130 5 0 0 131-135 5 0 0 136-140 5 1 0.2 141-145 5 0 0 146-150 5 2 0.4 151-155 5 0 0 156-160 5 0 0 161-165 5 0 0 166-170 5 4 0.8 171-175 5 0 0 176-180 5 1 0.2 181-185 5 4 0.8 186-190 5 3 0.6 191-195 5 4 0.8 196-200 5 7 1.4 201-205 5 3 0.6 206-210 5 6 1.2 211-215 5 4 0.8 216-220 5 2 0.4 221-225 5 1 0.2 226-230 5 0 0 231-235 5 1 0.2 236-240 5 3 0.6 241-245 5 1 0.2 246-250 5 0 0 251-255 5 1 0.2 Mean : ? ( all the frequency)/50 = 192 heartbeat per minute Median : (50+1)/2 = 25.5th term which lies in the group of 196-200 heartbeats per minute Mode: 212 heartbeats per minute Analysis The hypothesis is proved that on an average daphnias have heartbeats of between 190 to 200 per minute. This is shown by the histogram which I have plotted with the results collected above. ...read more.

Conclusion

Further equipment such as extremely accurate thermal probes, or other physical assessment tools would be necessary if conducting an extremely accurate investigation. Although the female daphnia population is in excess of the male, if a male daphnia was taken for the experiment it would make results differ due to the fact that it is difficult to distinguish male an female daphnia. They are identical except that males are generally smaller in size, have larger antennules, and the first legs have a stout hook use in clasping the female during mating. Rather than trying to identify males to detect stressful environments, it would be much simpler to inspect the brood chambers of females, i.e. if a male daphnia was use, the results would differ greatly. Daphnia stress levels can also alter results, in as much as if the daphnia has a high blood pressure (hyper tension), it would be most likely that they will have higher heart beat than average. On one or two occasions it was impossible with the equipment provided to count the daphnia's heart beat. Neurotic sensors would be ideal for counting the BMP's of the daphnia's heart. Also factors such as the heat from the lamp of the microscope, raising the temperature must be considered, as it is known that daphnias do not thermo regulate. If a pipette was contaminated with another substance such as distilled water, this could cause interruption the daphnia's original environment, and some would struggle and could causes death. ...read more.

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1. ## Measuring the heart rate of daphnia

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