This experiment was designed to identify the effect of cold-water temperatures on the respiration rate of goldfish. The respiration rates helped to identify the goldfish as being ectotherms or endotherms. Organisms exchange gases with their environment through a process called respiration or breathing. Aerobic respiration, also known as aerobic metabolism, occurs when oxygen is taken into the body and sent to all its cells; the oxygen is then used to break down food for energy (White and Campo 2008).
Respiration can be experienced through several structures such as the lungs, tracheae, gills, and integument in order to obtain oxygen. All organisms that experience respiration are either endotherms or ectotherms. Ectotherms are animals that depend on their environment for body temperature. These animals respond to changes in their environment in order to maintain homeostasis, the stable, internal conditions of the organism. Animals that are warm-blooded and can regulate their body temperatures internally regardless of their environment are endotherms.
For ectotherms, regulating body temperatures can require more work. Those aquatic animals have adapted several techniques to stay alive. Larry Crawshaw explains that animals, both aquatic and terrestrial, seek to avoid stressful thermal environments or to compensate for the temperature change by mostly lowering the metabolic rate (1979). Lowering the metabolic rate allows certain enzymes to be produced and chemical reactions to happen within the fish that actually warms it up. While lowering metabolic rates are important, respiration regulation is also important.
Stephen C. Wood also believes that ectotherms need behavioral mechanisms for temperature control. These mechanisms could include slowing breathing rates to conserve energy and releasing certain chemicals into the body (1991). This brings to light the question of goldfish being ectotherms or endotherms, and how the fish cope with temperature changes. These questions were the basis of the experiment. The dependent variable for this experiment was the respiration rate of the goldfish, and the independent variable was the temperature of the water.
The null hypothesis is that the water temperature will not affect the respiration rate of the goldfish; furthermore, the change in the water temperature will not stimulate a change in the goldfish’s respiration. Likewise, the alternative hypothesis suggests that a change in water temperature will affect the respiration patterns of the goldfish, and therefore cause the goldfish’s breathing rates to slow down or speed up. Materials and Methods To begin, two 600ml beakers filled with 150ml of aged water were used as containment vessels. Two goldfish were then each separately placed into an individual beaker.
It was decided to refer to the beakers containing the goldfish as “Beaker 1” and “Beaker 2. ” The control fish was contained by Beaker 1, and Beaker 2 contained the fish that received the experimental testing. Two separate beakers were filled, one contained ice water, and the other contained aged water. Thermometers were then used to measure and record the water temperature of the control fish’s water and the temperature- stressed fish’s water. Then the group members practiced counting the number of breaths each goldfish made in one minute.
Goldfish breaths can be identified by each time the fish opens and closes its mouth or by the contractions of its operculum. After the breaths were identified correctly and recorded for the first temperature, ice water was added to Beaker 2 (temperature- stressed fish) until the temperature of the water decreased by 2°C. Simultaneously, aged water was added to Beaker 1 (control fish) to maintain equal water levels in both of the beakers. The new temperatures were recorded and the number of breaths per minute by both fish were counted and recorded.
This process was repeated five more times. Throughout the entire experiment, the water temperature in Beaker 2 ranged from 22°C in the beginning to 10°C at the end. Once the experiment was concluded, aged water was slowly added to the temperature- stressed fish in order to raise the temperature of its water. This helped to return its environment back to normal conditions. Results The respiration rate for the control goldfish ranged from 123 to 140 breaths per minute, which was not a significant change.
On average, the cold-water treatments caused a significant decrease in breaths per minute by the end of the experiment. The average the breathing rates of goldfish subjected to temperatures less than 22°C decreased from a rate of 96 breaths per minute at the start of the experiment, to 56 breaths per minute at the end (Figure 1). The experimental fish in Group #1 ranged from 115 to 50 breaths per minute. Overall, the control fish’s breath rates generally remained constant, and the temperature-stressed goldfish had rates that decreased rapidly from start to finish.
Figure 1. The effect of decreasing water temperature on the breathing rates of goldfish. Discussion At the conclusion of the experiment, the two hypotheses were reviewed. Because the water temperature did affect the normal respiration patterns of the goldfish, the null hypothesis was disregarded and the alternative hypothesis was accepted. From the results of this experiment, it was concluded that although other environmental factors could play a minute role in the respiration rates of aquatic ectotherms, temperature was a major factor.
From this experiment, biologists and scientists could conclude that freshwater fish, similar to the goldfish, become inactive during the winter months due to the drop in water temperature. However, the results of the experiment were concise, but several error could have occurred. For instance, all the fish were kept in the same aquarium before and after the experiment. This could have meant that some of the fish were diseased having their respiration rates already compromised. Also, the fish did not remain calm long enough to get an accurate measurement of its respiration rates.
Clearly, a more accurate experiment could have taken place had there been several more groups participating in the experiment. To further clarify the hypothesis, the experiment could have been adapted to also measure the metabolic rate of the goldfish. The fish would need to be tested for their readiness to eat in different temperatures. This means that the fish would need to be tested for a much longer time period, and the fish would need to be hungry every time they were tested or else the experiment would be compromised.
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