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Daphnia project.

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KIERON HARPER DAPHNIA PROJECT Introduction One of the most common inhabitants to be found in lakes, ponds and quiet streams are Daphnia (Also known as the water flea). Daphnia are usually less than 3mm in size and are closely related to Crab and Shrimp, and therefore a crustacean. Daphnia are commonly so called "Water Fleas" due to there erratic jumpy swimming motion through the water, caused through there second antenna being thrust downwards. Daphnia are vital elements of the food chain in fresh water areas, as they are a staple diet of small and large fish alike, and keep the water clear as part of the vital plankton feeding community. Daphnia feed on bacteria, yeast, micro-algae, detritus, and other organic matter. Their limbs draw water, which contain food particles towards their mouths. Before being swallowed the food passes through sticky mucus in the mouth entrance, which is used to mesh the food. Daphnia are predominately asexual; therefore population is usually made up of females, who asexually reproduce. They can produce broods every two - three days, with more than one hundred eggs per time. It is possible for one female too have up to twenty-five broods in a lifetime. They can also sexually reproduce under adverse conditions, in such times males are produced and sexual reproduction ensues. High population growth, low temperatures, low oxygen supply or lack of food brings about this type of sexual reproduction. The result of this being, the laying of resting eggs, similar to brine shrimp. A daphnia is a cold-blooded organism, also known as ectothermic, which means its survival is based on its surroundings. ...read more.


Place another cover slip over the top making sure the Daphnia are unharmed. 3. Place the cover slips under the water in the Petri dish. 4. Place the Petri dish on the stage of the microscope and look at the Daphnia. 5. Find the heart of the Daphnia and practice counting heartbeats. 6. Measure the temperature of the water accurately and count the heart rate for one minute using the calculator in the aforementioned manor. 7. Draw off some of the water and add water of temperature 200C. 8. Once the water has been mixed, measure the temperature again to make sure it's correct. Count the heart rate again. 9. Repeat the above steps again incrementing the temperature by 50C until it reaches 350C. Risks There are several factors that can alter the health of Daphnia and may even cause them to die. These include: * Oxygen. Daphnia can survive in poor water conditions. They have the ability to make haemoglobin, which enables them to survive in an oxygen poor environment. * pH &Ammonia. Daphnia need the pH of the water to be between 6.5 and 9.5. High Ammonia and pH will reduce the levels of reproduction, but will not actually cause any harm to the Daphnia. * Minerals. Daphnia are very sensitive to the composition of their environment. Salts such as sodium, potassium, magnesium and calcium can cause the Daphnia to become immobile and they will eventually die. Variables There are several factors, which need to be taken into account whilst studying the Daphnia: * Firstly the oxygen levels must be kept constant, to prevent the Daphnia from suffocating. ...read more.


The impact of these factor, cause me to doubt the validity of my results. I would like to repeat this experiment several times taking into account these additional points: * The use of microscopes which did not omit heat * Use a higher powered microscope * Use Vaseline to keep the daphnia still With these points taken into consideration and the opportunity to repeat the experiment several times, would I be totally confident in my results and findings. Only with the repetition, can an experiment be truly validated. The Daphnia as an ectothermic organism which uses its surroundings to regulate body temperature, would in its natural habitat, be able to cool down by travelling to the bottom of its body of water. Thus in turn, keeping its body at its optimum temperature. In this experiment the Daphnia could not escape the heat as it was confined to the Petri dish, and had to use different ways to cool down. This led to the increase in heart rate as the Daphnia produced a lot of energy as it fought to bring its body temperature under control. Overall I think the experiment was successful, given its limitations. Which I would change given the opportunity to reattempt the experiment. **www.can.uni.edu I Temp in 0C 15 20 25 30 35 Daphnia 1 4.58 1.73 6.25 6 3.51 Daphnia 2 6 6.93 7.94 4.58 4.86 Daphnia 3 9.17 6.93 7.55 30 1.53 If standard deviation is small it shows a small spread of data therefore the data is quite accurate. If standard deviation is large it shows a large spread of data therefore the data is inaccurate. Looking at the error bars on the graph shows this. Kieron Harper 1 ...read more.

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