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To investigate the effects of a depressant on the heart rate of a daphnia.

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To investigate the effects of a depressant on the heart rate of a daphnia. Background information Daphnia-What are they and Why use them for Science? Daphnia are also called water fleas. The most common type is called Daphnia pulex. They are are part of the Crustacean group and can be found in lakes, ponds and small streams. The water that they live is full of nutrients, which is called eutrophic. Daphnia are used quite a lot in scientific research and are interesting animals for study under the microscope. They are covered in a transparent shell and all internal organs can be seen which makes it good animal to experiment with. You can also see the beating of its heart. This is very helpful in our experiment, as we need to record the heart rate. Most daphnia are herbivores. Most daphnia feed on bacteria and very small algae. However not all daphnia are herbivores there are some predators such as Polyphemus pediculs. ...read more.


* Slide cover- To cover the daphnia in the cavity and prevent escape during examination * Pipette- To insert the ethanol on the slide * Syringe- To collect the daphnia and to insert them onto the slide * Beaker- To keep the daphnia in prior to examination * Timer- To count time Step-by-step plan 1. Collect and set up equipment. 2. Select daphnia and extract to slide using syringe. 3. Soak up excess water using a paper towel to prevent ethanol being diluted. 4. Add 5 drops of ethanol to the daphnia on the slide. 5. Place cover on slide. 6. Add the slice to the microscope and begin counting for 30 seconds 7. To measure the number of beats I will bang my fist on the table for every heartbeat and my partner will record the amount of bangs that he hears. 8. Repeat this experiment for the different denominations of ethanol. They are- 0.0%, 0.2%, 0.4%, 0.6%, 0.8%, 1%. 9. Record the results in a suitable table. ...read more.


Our prediction was true in a sense. Although it was proved wrong, as explained in the conclusion, I will now explain why it was incorrect. The influx in he heart rate could be for a number of reasons. One reason could be unnecessary stress to the daphnia, and different states of health. Another reason could be miscounting the hearts beats on my part. If I was to do this experiment again, I would try to use a more accurate method of measuring the heart rate. Another improvement could be a more accurate way of delivering the ethanol to the daphnia and the daphnia to the slide. Again as I mentioned in the conclusion, it is important that we obtain the same kind of daphnia. It is unfair to use larger, older daphnia than smaller, younger ones. This would obtain different results. A method of vetting the daphnia beforehand would have to be introduced where only daphnia of the same size are used. By doing this, then a more accurate set of results would be obtained. Sonny Kumar Science Coursework Biology ...read more.

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