Introduction
This report discusses an experiment conducted to examine the rate of aerobic cellular respiration in aquatic organisms. The study focused on Elodea (an aquatic plant), snails, and goldfish. Carbon dioxide production was monitored as a measure of respiration. Each organism, being ectothermic, was placed in covered beakers resulting in varying amounts of carbon dioxide production. The main goal of the experiment was to determine and compare the rates of cellular respiration among these three aquatic organisms.
Aerobic respiration occurs in the mitochondrion of a cell and involves using glucose and oxygen to obtain energy. This process produces carbon dioxide, water, and ATP as energy (Hoefnagels, 2012). According to Biology 6th Edition’s research findings, plants utilize light to convert atmospheric CO2 into carbohydrates (Johnson, 204). Given this information, I predicted that the snail would respire at a faster rate and produce more carbon dioxide due to its heavier weight in comparison to the other two organisms.
Methods
Four beakers, labeled 1 through 4, were filled with 100 mL of aerated distilled water. Each beaker was then weighed to the nearest 0.01 g. In beaker #1, a goldfish was placed in 100 mL of water. In beaker #2, a snail and an empty snail shell were placed in 100 mL of water. In beaker #3, an Elodea measuring 8 cm was placed in 100 mL of water. Beaker #4 remained empty. The weight of each organism was determined by subtracting the initial weight from the total weight after placing them in the respective beakers.
To block out all light, aluminum foil completely covered all four beakers and they were left undisturbed for one hour.
After one hour, four flasks labeled as numbers 1 through 4 were prepared. The fish and snail were returned to their original locations while the snail shell and Elodea were also put back where they belonged.
Using a graduated cylinder, 25 mL of water from beaker #1 was measured and transferred into flask #1; this process was repeated for each subsequent pair: beaker #2 into flask #2, beaker #3 into flask #3, and finally beaker #4 into flask#4. The remaining water in the original four beakers stayed untouched until all necessary data had been collected.
4 drops of phenolphthalein were added into flask #4 and swirled. The flask was then placed on a white paper (background). NaOH was added drop by drop, with each drop being counted. After each drop, the flask was swirled until the solution turned into a faint pink color. The same process was followed for flask #1, flask #2, and flask #3, with 4 drops of phenolphthalein being added and swirled before adding NaOH drop by drop and swirling the flask after each drop until the solution turned into a faint pink color.
Results
The organism’s weight can be determined by subtracting the weight of the beaker and water from the combined weight. The goldfish weighed 4.1g (231.1-227), the snail weighed 4.8g (238-232.3-0.908(snail shell weight)), and the Elodea weighed 4.1g (229.2-225.1). According to Table 2, in flask #1 (goldfish), 19 drops/25 mL of NaOH were added, which is equivalent to 76 drops/100 mL or 3.8 mL when converted from drops to milliliters by dividing by 20. The goldfish had a carbon dioxide rate of production of 0.61 during an hour.
In flask #2 (snail) and #3 (Elodea), the same number of drops of NaOH (12 drops/25 mL) were added, which translates to 48 drops/100 mL . However, there were different respiration rates for the snail (-0.21) and Elodea (-0.24). The formula provided in instruction 14 p.Lab7-3 was used to calculate the rate at which carbon dioxide was produced.
Conclusion
Despite my initial belief that the weight of a snail would have a greater impact on its CO2 production compared to other aquatic organisms, I was mistaken. The fact is that an organism’s weight does not affect its CO2 production. We measured the weights only to ensure that we were comparing organisms of similar sizes. It is clear that if we were to compare a large elephant with a small mouse, the elephant would produce more CO2. Our hypothesis was proven incorrect because the snail was deceased and therefore unable to produce any CO2. Conversely, Elodea is a plant that undergoes photosynthesis, utilizing CO2 in this process (C H O + CO O + H O + energy). As goldfish engage in aerobic respiration, they generate more CO2 than Elodea as a byproduct. If I were to conduct this experiment again in the future, I would select a live snail so that I could compare the CO2 production between goldfish and snails.
References
- George, B. J. (2002). Photosynthesis. In Biology (6th ed.). (pp. 183.204). Retrieved from http://highered.mcgraw-hill.com/sites/0073031208/
- Hoefnagels, M. (2012). Science, Chemistry, and Cells. In Biology Concepts and Investigation (2nd ed.). (pp. 107). New York: McGraw Hill Compamies, Inc.,
- King, B. et al. (2007). Lab 7: Cellular Respiration. In General Biology: Study Guide and Laboratory Manual (10thed.). (pp. 14). NVCC Alexandria: Pearson Custom Publishing.
