The Ability of Daphnia magna to Maintain Homeostasis Despite Varying Toxicity Levels of Surrounding Environments

Transcription

1 The Ability of Daphnia magna to Maintain Homeostasis Despite Varying Toxicity Levels of Surrounding Environments By: Kayla, Kenyana, Erin, and Paulina Mr.Scheman 1 st Period Daphnia magna Lab Purpose: In our experiment we were studying the Daphnia, a small crustacean that resides in ponds, and its ability to maintain homeostasis. (Homeostasis is a creature s capability to maintain its internal conditions despite the conditions around it.) We tested putting them in different solutions with different toxicities in order to count the heart rate and make our observations to form a conclusion.

2 Research: Daphnia are small, planktonic crustaceans, between 0.2 and 5 mm in length. Daphnia comprises about 150 species and Daphnia magna is one of them. Daphnia magna comes from the animalia kingdom. They come from the Daphniidae family. Daphnia are filter feeders, and eat bacteria and small detritus and algae particles.their environment can range from acidic swamps to freshwater lakes, ponds, streams, and rivers. Daphnia reproduce parthenogenetically usually in the spring until the end of summer, with one or more of the babies fed inside the carapace. When hatched, Daphnia must molt several times before they are fully grown. Fully grown female Daphnia are able to produce a new brood of young about every ten days under good conditions. Males are much smaller in size than the females, and possess a specialized abdominal appendage. Daphnia lifespan can not exceed one year.they are largely temperature- dependent.daphnia may be used in certain environments to test the effects of toxins in an ecosystem, which makes them on indicator genus, particularly useful for its short lifespan and reproductive capabilities. Because they are nearly transparent, they are easy to study their organs while live specimens. Hypothesis: Day One: If a Daphnia is placed in a solution other than pond water then it will negatively affect the creature by either increasing or decreasing it s heart rate. Day Two: If a Daphnia is placed in a solution with a high glucose content then the creature s heart rate will increase as the glucose content does. Data: Solution Daphnia and Homeostasis Lab Day 1: Reaction Pond Water (Control Group) 258 beats per minute Looks brown, fast heartbeat Wiggling fins move at rhythmic pace

3 Sugar Water 252 beats per minute Brown and heart beats are slower Starch 318 beats per minute Turned shade of yellow Not wiggling as much Vinegar 192 beats per minute Distilled Water 174 beats per minute Revived it from vinegar Fins moving slowly Coffee 276 beats per minute Same color Moving rapidly Depressant Made heartbeat uneven 282 beats per minute Jerky movements Honey 288 beats per minute Daphnia Lab Day 2: Percentage Heart Beats Per Minute 0% Honey 100% water (control group) 144 beats p/m 75% Honey 25% water 144 beats p/m

4 50% Honey 50% water 144 beats p/m 25% Honey 75% water 144 beats p/m 10% Honey 90% water 130 beats p/m Procedure: Day 1: 1 First we measured and recorded the Daphnia s heart rate when it was just in pond water so we would have a control group to compare our other data to. 2 Then we slowly replaced the pond water with an equal amount of our first test solution, and recorded the heart rate along with other notes about how the creature acted in that solution. 3 We repeated that the process of the 2nd step with all other solutions that we placed the Daphnia in. To figure out how the percentage of a substance in a diluted form can affect the heartbeat of Daphnia we formed a simple experiment. In order to figure out the percentage we had to keep track of the ratio of water to the substance. Our assigned substance was a honey solution. Day 2: 1 First, we measured the heart rate of the Daphnia in it s usual pond water so we could have a control group. 2 Then, we diluted a honey solution so it was only 75% solution and 25% water and replaced the pond water with an equal amount of it then measured and recorded the heart rate. 3 We then repeated the above step with more dilutions of the honey solution, decreasing the amount of honey content put into the solution as we went and recording our results. Analysis: According to our Day 1 test results, the Daphnia were affected by the different solutions greatly. The starch, coffee, honey and depressant all increased the heart rate, while the sugar water, vinegar and distilled water all decreased the heart rate. The fact that the heart rate ranged from anywhere from as low as 174 beats per minute to as high as 318 beats per minute while the daphnia did not die, leads us to believe that they are reasonably good at adapting to their environment in order to maintain homeostasis. According to our Day 2 test results, the Daphnia were not greatly affected by any percentage of honey solution. After looking over the data collected we observed that no matter how diluted the solution was the heart rate, measured in beats per minutes, didn t change that

5 much. Although we did observe that when we diluted the substance down to only 10% honey the heart rate changed to 130 beats per minute as opposed to the usual 144, allowing room for error, we felt it didn t affect the overall data collected much at all. The heart rate of our test subject did not increase or decrease by anything exponentially at any point and it seemed to be content the whole time. Conclusion: Our hypothesis for Day 1 stated that any change in environment would either increase or decrease the Daphnia s heart rate. This hypothesis was correct. During our experiment we saw the heart rate ranged greatly when the Daphnia was put into different environments. However, we noticed when comparing our data from Day 1 and Day 2 that the honey effected it differently for each experiment. This could have been an effect of, when during our Day 1 testing, placing the Daphnia straight from one solution into another without placing it in water in between each in order for it to reset so to speak. If this is truly the cause of our conflict then it is simply fixed by redoing the experiment, however, this time adding a step in between each transition of solutions in which the Daphnia would be placed in water for an allotted time in order to return to it s normal heart rate. Besides that small detail, we feel that Day 1 was a success since we managed to keep our Daphnia alive the entire way through as we collected our data. Our hypothesis for Day 2 stated that as the honey percentage in the solution increased so would the heart rate of the Daphnia. This hypothesis was proved wrong by our data. Our data showed us that no matter how diluted the solution was it really had no effect on the creature s heart rate. The only number that was different than the others was when the percentage of honey in the solution was 10% and it was only off by a very small number. We feel that the glucose in the honey did not affect the Daphnia very much, and that they were quite content in that environment no matter how much honey was present. This experiment could have been improved, along with Day 1 as well, by counting the heart rate for each situation multiple times, just so you have a better and more accurate set of data. Overall, this experiment was a success despite our incorrect hypothesis, because it provided us with data enough to make a new, corrected, and better hypothesis than before along with another experiment and more sets of data. *No Daphnia were harmed in the making of this lab.*