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Effect of Ethanol on the Daphnia heart rate

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Introduction

Effect of Ethanol on the Daphnia heart rate In this experiment we will be looking at the effects of different concentrations of ethanol on the heart rate of the water flea, Daphnia. This small freshwater crustacean is relatively transparent; this allows their heart rate to be recorded clearly by simply observing them through the microscope. The experiment consists in preparing 5 different environments to put the water flea in, and observe how the heart rate responds to each change; the change will be the increase of ethanol concentration %. This will be the independent variable. The dependent variable is the heart rate of the Daphnia. The materials needed to perform this experiment are the following: * Normal size syringe * 2 Small syringes (must have units of measurement) * Open top pipette * Ethanol of 1% concentration * *Various Daphnia to perform experiment on * Microscope * 6 Petri dishes * Cavity slide * Marker * Paper * Stop watch * Distilled water * Labels *Before performing the experiment you will have to go to a pond or lake, and acquire a significant amount of water fleas and place them in a glass or container in water from the pond or lake. ...read more.

Middle

Multiply this number by four; this gives you the heart rate per minute. Record the result. Do this process 3 times in order to get 3 heart rates. Add the 3 heart rates and then divide the result by 3; this will give you the average of the Daphnia heart rate under those conditions. Keep the Daphnia under the microscope for a maximum of 2 minutes, because the heat of the light in the microscope could have effects on the experiment. Turn the microscope off after the count to prevent further heating caused by the light. 7. Remove the slide from the microscope, and with the normal size syringe put the Daphnia into the 0.2% labelled Petri dish (wash the slide with water and dry it). Leave the Daphnia in the Petri dish for 3 minutes once again. After 3 minutes, use the normal sized syringe to put it onto the microscope slide. Repeat step 6 and record results. 8. Count the heart rate of the Daphnia when placed in all the concentrations. Work your way up from 0% to 0.2% to 0.4%, 0.6%, 0.8%. ...read more.

Conclusion

They allow communication between cells to occur. Nerves can receive communication from cells far away or from nerve cells near by. Cells far away secrete hormones, which find their way to the target nerve's hormone receptors. Once these hormones attach to the receptor, changes in the nerve take place. The hormone-receptors, when activated, can change how quickly a nerve generates an impulse, or alter how fast the nerve passes impulses along. Some hormones increase heart rate and some decrease heart rate. Other receptors allow communication between adjacent nerve cells (such as between the pacemaker neurons and the follower neurons). Instead of hormones, the receptor binds to neurotransmitters. These receptors sometimes accidentally bind molecules they shouldn't. The nerve fibers conducting pulses to the hearts of Daphnia may contain receptors that inappropriately bind to the ethanol causing a decrease in activity. This process coincides perfectly with the fact that ethanol is a depressant that decreases nervous activity, partly through interfering with neurotransmitters, and in turn decreasing heart rate. In conclusion, increased levels of ethanol affect the regulation of heartbeat in Daphnia. As the concentration of ethanol increases, the heart rate decreases and patterns can be seen as to how the rate responds to changes in the environment. The Daphnia heart rate decreases in an average of 9 b/m as the concentration increases by 0.2%. ...read more.

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