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Ammonia Excrfetion As A Function Of Body Size In Cray Fish Essay, Research Paper

Ammonia Excretion As A Function Of Body Size In Crayfish INTRODUCTION The breakdown of proteins and nucleic acids during metabolismgives rise to excess nitrogen which must be rid of by living organisms. Aquatic animals, such as the crayfish we studied in lab, the excess nitrogen is excreted in the form of ammonia (NH3) Because ammonia is highly soluble in water, the ammonia is able to be excreted across the gills into the water. The rate at which this takes place is related to body mass of the organism. In this lab, we measured the rate of excretion of ammonia in two crayfish of different sizes, as well as in experimental water. A calibration curve of ammonia concentrations was used to calculate the mass specific ammonia excretion rate from the change in ammonia concentration per unit time, the volue of water and the mass of the crayfish. Graphs were also constructed to show the excretion rate of the large and small crayfish. Material and Methods The experiment was performed as described in Experiment 2 in theBio 114 lab manual on pages 710. Results In the first table, we found the absorbance at 650nm on the Spec20 of our solutions (tap water, and four standards, 25, 50, 75, 100 Umole/L). To each tube we added .2 ml of alcohol phenol and .2 ml of the sodium nitrprusside reagent, and .5 ml of oxidizing agent. This reaction should have taken around 30 minutes, but happened sooner than expected (about 10 minutes). The first graph is the calibration curve of ammonia concentration (xaxis) and absorbance (yaxis). This enabled us to determine the ammonia concentration in the big crayfish water (77), and for the smaller crayfish water (53). Using the formula in the lab manual, we calculated the rate of ammonia excretion for both crayfish. Rate of the small crayfish was 42.898 mmole/kg/h. Rate of the big crayfish was 29.4 mmole/kg/h. The next graph constructed plotted the logs of the crayfish masss and excretion rate. Mass Log Mass Am. Excretion Log Am. Ex S= 21.34g 1.33 42.898mmole/kg/h 1.63 B= 29.40g 1.47 29.4 mmole/kg/h 1.47 We then plotted a graph with log mass on the x axis and the log ammonia excretion on the Y axis. The calculation of the gradient is as follows: n=1.471.63= 8/7. Conclusions: Due to the surface area, the rate of oxygen consumption is muchhigher in the small animal than in the large. It has been learned that surface area of the body directly affects many rates of life processes. Our results showed that the small crayfish absorbency was indeed higher than that of the larger crayfish. This is directly the result of the smaller crayfish having lesser mass. The inverse is also true that the larger crayfish had a slower rate of excretion in relation to the smaller crayfish because the larger one had a larger mass. 1.471.33

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