|MadSci Network: General Biology|
Hello Natasha! Thank you for your question. You asked: "I am currently doing a biology project studying the effects of different oxygen levels on Daphnia. To carry out my experiment, I will measure the heart rate of at least 5 Daphnia at certain intervals, each 5 Daphnia from one of the six different oxygen levels made up. I need information for my formal write up of the experiment and am finding it very difficult to find direct info on how oxygen levels effect Daphnia. My hypothesis is that lower levels of oxygen increase the heart rate of Daphnia. What happens if the heart rate is increased? How do Daphnia take oxygen in and use it? etc. It would also be of great help if you know of any similar experiments carried out." Sounds like you're on your way to a good experiment! First off, let's see how your study looks as an abstract (which is simply a brief summary of your experiment). An abstract generally follows a format containing a set of steps: 1. Title 2. Background (Why are you doing this project? What is your main goal (your hypothesis))? 3. Methods (What are you going to do to the Daphnia in order to find out if your hypothesis is correct?) 4. Results (What did you find out? What were the heart rates of your Daphnia at each oxygen level?) 5. Conclusion (Did your experiment prove that your hypothesis was correct? (it's OK if your hypothesis was wrong --- it is still data...) Did you observe other changes that you had not expected to find?) Now, let's examine each step: The Title will come last once you have acquired your data and come to a conclusion about your experiment. As for the Methods, you seem to already know how you are planning to carry out the experiment (writing up the Methods section tends to be the easiest part for all researchers, as you are simply describing what you have already done). Once you perform the experiment, the results will come easily as well. Even the data you acquire is completely the opposite of what you expected, or if all your Daphnia die tragically, or if you observe no changes whatsoever in any of your groups, your data is still data and needs to be presented. The Conclusions will basically discuss how well your hypothesis stood based on what you and others already know about Daphnia physiology (specifically obtaining to their heart rate responses at different oxygen levels), and what you observed during your experiment. So, based on your question, you seem to still need the following for your Background: 1. More info on Daphnia physiology 2. More info on what others already know regarding Daphnia physiology (specifically obtaining to their heart rate responses at different oxygen levels) I did some searches on the net and found a bunch of different websites for you which may spark some theories for you to play around with: www.killifish.vrx.net This site mentions that as water temperature rises, water loses its ability to carry dissolved oxygen... (Hint: Think of opening a warm soda can as opposed to a cold soda can... Which fizzes more?...) www.caudata.org/daphnia This site mentions that Daphnia are able to synthesize a particular molecule in an oxygen-poor environment... (Hint: What molecule carries oxygen? What do Daphnia eat...therefore, what type of water are Daphnia most often found in?) www.internal.eawag.ch/~spaak/papers/lass_et_al_2000.pdf This site is a paper by S. Lass and colleagues entitled "How do Migrating Daphnids Cope with Fish Predation Risk in the Epilimnion under Anoxic Conditions in the Hypolimnion". (You can also access this paper in the Journal of Plankton Research Vol 22 No.7, pages 1411-1418, 2000). (Hint: What eat Daphnia?...do they use their eyes to find the Daphnia?...if so, can the Daphnia hide in darker waters to avoid getting eaten?...doesn't the water get darker as you go deeper?...however, how are the oxygen levels in the water as you get deeper?...therefore, are there Daphnia surviving in this part of the water?...if so, how can they?...are they unhealthy here?) Searching the MadSci website for more information on Daphnia will provide information on Daphnia physiology, including heart rates during various conditions. www.daphnia.com provides ton of general information and many links to other Daphnia websites that range from raising Daphnia for pet food to examining Daphnia populations in water-quality research. Hope this helps! Feel free to email me at firstname.lastname@example.org if you have further questions as you progress with your research project. I am also very interested in hearing how your study turns out! Please keep me posted on what you discover! Sincerely, G. Monreal
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