Investigating How Temperature Affects The Breathing Rate Of Goldfish
The aim of this experiment is to find out whether varying temperature of the surrounding environment of a goldfish would affect its breathing rate. Research question
Does the breathing rate of goldfish change with changes of the surrounding temperature? If it does, how does it? Would increasing the temperature of water containing a goldfish lead to high breathing rates or vice versa? A beaker containing aquarium water will be used as the environment in which a goldfish will be placed. The temperature of the water in the beaker will be altered successively by serially adding crushed ice to obtain six temperature conditions: 20°C, 18°C, 16°C, 14°C, 12°C, and 10°C. A goldfish will placed into the beaker at each temperature condition. After allowing the fish to acclimate, the temperature will be taken and the number of breaths of the goldfish per minute counted. In this case, the stop watch will be used. When a graph of number of breaths per minute against temperature is plotted, the gradient shows the magnitude of the extent of change in breathing rate of the goldfish per unit change in temperature. This can be used to establish the relationship between the rate of breathing of a goldfish and temperature. It is expected that the slope of the graph would be positive. This implies that as the temperature is raised, the breathing rate is also expected to increase.
If temperature of water is lowered, then the breathing rate of goldfish should fall and vice versa. This is mainly due to the fact that the metabolic functions of the goldfish drop whenever the temperature of the surrounding environment decreases. Besides, more dissolved oxygen is available in cold water than in warmer water. Consequently, goldfish does not have to breathe faster in order to be able to absorb enough oxygen. Variables
The variables for this experiment were categorized into three groups: dependent variables, independent variables, and controlled variables. The independent variable for the experiment was temperature. On the other hand, breathing rate was taken as the dependent variable. Several conditions that could affect the breathing rate of goldfish formed the category of controlled variables. These include crowding, oxygen concentration, size of the goldfish, and effects of acclimation.Control of variables Overcrowding was controlled by putting one goldfish in the beaker at each temperature condition. Size was controlled by using the same goldfish throughout the experiment. This ensured that the size of gold fish was maintained. The goldfish was also let to stay in the beaker for some time in order to acclimate each time the temperature of water was lowered. This helped in ensuring that the fish adapts to the environment and the breathing rate becomes steady.
Materials & Methods
The methods and materials used are explained below.
Materials used in the experiment are the following: a clock, thermometer, one 200mL beaker aquarium water, and crushed ice.Method
First, the students determined the quantity of ice cubes to be added to the water in order to reduce its temperature by 2.0°C. This was practiced severally. Ice cubes were added to 100.0mL of aquarium water contained in a 200mL beaker. After practicing, the beaker was emptied and then refilled with aquarium water. The amount of water with which it was refilled was the same as the amount used for testing temperature change, 100.0mL. A goldfish was dipped into the aquarium water in the beaker. The Goldfish was left in the aquarium water to acclimate before a temperature of 20.0°C was recorded. The students then set the stopwatch and counted the number of breaths taken by the goldfish in one minute. The number of breaths was determined by counting the number of times the operculum moves in and out. The results were recorded on a table. Next, enough pieces of ice cubes were added to lower the temperature of the aquarium water by 2.0°C to 18.0°C. The water was then stirred to achieve a uniform temperature throughout the water. The fish was left to adapt to the new temperature for sometimes. Then, the stopwatch was set and the number of breaths of the goldfish in one minute counted. The results were recorded on a table. This procedure was repeated several times; whereby the number of breaths per minute in five trials at each temperature was obtained; until the temperature of the aquarium water was lowered to 10.0°C. Next, aquarium water was added to the beaker with the goldfish to enable the fish recover. The fish was then returned to the aquarium. The exercise was repeated twice in order to minimize random errors.
While the goldfish was being used in the experiment, the students ensured that the aquarium water in the beaker remained unchanged. This was meant to ensure that the number of organisms in the water remained constant throughout the experiment. In order to ensure that the content of the aquarium water remained unchanged, the experiment was carried out in a room with still air so that microorganisms could not be swept into the beaker by wind. Only one goldfish was used in the entire experiment so that variation in rate of breath that may be caused by using different gold fishes of different sizes at different temperature conditions would be eliminated. The goldfish was also let to stay for sometimes in order to adapt to new temperatures whenever ice was added to aquarium water in the beaker. This was meant to allow the breathing rate of the goldfish to increase and then drop to a steady value.
The number of breaths per minute of the goldfish counted at each temperature was obtained. Since the experiment was done in five trials, there were five values of the number of breaths per minute at each temperature condition. These are shown here:
At (0.5±20°C) (0.5±20°C) (0.5±20°C) (0.5±20°C) (0.5±20°C) (0.5±20°C)
Trial 1 (130) (113) (80) (67) (54) (46)
Trial 2 (104) (86) (74) (56) (52) (42)
Trial 3 (137) (119) (82) (60) (52) (44)
Trial 4 (120) (117) (92) (74) (67) (47)
Trial 5 (121) (119) (92) (57) (54) (46)Uncertainty
The instruments used in the experiment exhibit certain degree of uncertainties. The table below shows the uncertainties for the quantities measured in the experiment.
It was observed that whenever the temperature of the aquarium water was lowered by 2°C, the number of breaths of the goldfish per minute also dropped. However, the magnitude of the drop of the number of breaths of the goldfish per minute due to a reduction in temperature by 2°C was not constant in all the temperature conditions used. However, there was a steady drop in the number of breaths of the goldfish per minute as the temperature was also steadily lowered. At 20°C, the average number of breaths per minute was 122. In all the trials, the number of breaths per minute was highest at the temperature of 20°C. On the other hand, the number of breaths per minute was lowest at 10°C, which is the lowest temperature condition created in the experiment. The average number of breaths per minute at this temperature is 45. The rate of change in number of breaths per minute of the goldfish was observed not to be constant. Instead, some trials showed higher rates of change than others. This means that slopes of the graphs of breath rates against temperature would differ from one trial to another. It was also observed that immediately the goldfish was put in the aquarium of water in the beaker, it breathed faster. However, the breath rate slowed down until the goldfish could breathe at a steady rate. Similarly, whenever ice cubes were added to the aquarium water in the beaker so that the temperature drops by 2°C, the goldfish would start breathing faster. However, its breathing rate dropped slowly until it could breathe steadily. Bubbles of air could also be seen moving from the bottom of the beaker to the top. It was also observed that the goldfish moved more actively in the aquarium water at warmer temperature than at cooler temperature.
When a graph of breath rate against temperature is plotted, it is found that temperature is directly proportional to the breath rate. The graph below shows the relationship between the rate of breath of the goldfish and the temperature of the aquarium water.
Figure 1: The relationship between breathe rate of gold fish and temperature
This relationship can also be shown for all the trials done. The table below shows the relationship between breath rate of the goldfish and the temperature of the aquarium water in the beaker.
Figure2: graph representing the relationship between breath rate of goldfish and temperature of the aquarium water for the five trials done in the experiment.
Figure 1 above shows that as the temperature of aquarium water in the beaker increases, the breath rate of fish also increases. A line of best fit is used to show this relationship. The slope of the graph represents the average change in rate of breath per unit change in temperature.
Since the value of the slope is 8.7143, it follows that a change of the temperature of water by 1°C would cause an average change of breath rate of the goldfish by 8.7143 breaths. In figure 2, the relationship between breath rates and temperature of the aquarium water is shown for the five trials. Trial 2 shows the steadiest slope of all the trials. However, both graphs show that the change in breath rates is directly proportional to change in temperature.
The results of the experiment show that increasing the temperature of the surrounding of goldfish would increase its rate of breathing. On the other hand, lowering the temperature of the environment of the goldfish would lead to a drop in its rate of breathing. There are two explanations for this phenomenon. First, when temperature of the surrounding environment rises, metabolic activities of the organism rise. Goldfish is an aquatic organism. Consequently, it is a pikilotherm. Poikilotherms are organisms, mostly aquatic ones, whose body temperatures change depending on the change in the surrounding temperature. In pikilothrems, a rise in the temperature of the external environment triggers metabolic activities that help ensuring that there is balance between the external environment and the internal environment in terms of temperature. The metabolic activities are aimed at promoting processes that are exothermic in order to raise the temperature of the internal environment to the same level as the temperature of the external environment (Perry, 53). Consequently, the demand for oxygen rises. Oxygen is needed to drive the activities. In order to meet the demand, the body system of the goldfish triggers high rate of breathing. This was observed through the frequency of movement of the fish’s operculum.
Another explanation for the reduced rate of breathing as a result of lowering of temperature of the aquarium water is that cold water usually has more dissolved oxygen than warmer water (Hughes, 234). Consequently, more oxygen is available and accessible to the goldfish in cool water than in warmer water. The fish does not have to breathe faster in order to supply the body with adequate oxygen. Instead, the goldfish breathes normally and is able to supply the body with adequate quantity of oxygen.
Movement of the operculum observed during the experiment shows the process of gaseous exchange in the fish. The bubbles seen moving from the bottom of the beaker upwards show that gaseous exchange was taking place in the goldfish.
Results differed slightly from one trial to another. This might be due to certain errors associated with various measurements taken. For instance, the accuracy with which students can start counting the number of breaths of the goldfish at the same time timer is started is not 100 percent. Error is involved in this case. Besides, inability to start the stop watch and counting at the same time in all the trials causes errors. Another source of error could be failure to allow the fish to acclimate immediately the temperature of the aquarium water is lowered before determining the breath rate. The errors involved can be grouped into two broad categories: random and systematic errors. Failure to allow the goldfish to acclimate is a systematic error. It can cause deviation of the results from the actual value by a constant magnitude. For instance, it can cause the rate of breath to be higher. Random errors are associated with the precision of the instruments used and factors intrinsic to the goldfish. For instance, the metabolic activities of the goldfish can change due to slight changes in the aquarium water.
The results of the experiment show that lowering temperature of the surrounding water of the goldfish leads to decrease in the breath rate of the goldfish. The hypothesis of the experiment; which states that if the temperature of water surrounding the goldfish is lowered, the breath rate increases; is accepted. The gradient of the graphs showing the relationship between the breath rate of the fish and temperature in the five trials clearly explain that the higher the temperature, the higher the rates of breathes of the goldfish.
Both random and systematic errors were involved in the experiment. With regard to random errors, changes in tissues of the goldfish as well as other metabolic processes might have led to the different number of breaths per minute observed in each trial. Besides, physical changes of the instruments such as expansion due to changes in temperature can cause errors. Possible sources of systematic errors in the experiment are inaccurate thermometer, stopwatch, and beakers. Systematic errors can result into results with values that deviate from the actual value by a given magnitude. They lead to results that also deviate from the actual value by definite value. For instance, stop watch that is 0.05 seconds behind would lead to recording of more number of breaths per minute than stopwatches that record time normally. Some steps in the procedure could result into an error. For instance, addition of ice balls cannot lower the temperature of aquarium water by 2°C accurately. Besides, after addition of ice, the temperature may not remain constant due to external environmental influence.
Adequate efforts were made to contain the controlled variables. For instance, the fact that the fish was not taken from the beaker every now and then helped to minimize errors. However, there is need to improve the means of changing the temperature of the aquarium water so that accurate temperature is obtained.
HOAR, W. S., RANDALL, D. J., & CONTE, F. P. (1969). Fish physiology. New York, Academic Press.
Hughes, G. M., & International Congress of Physiological Sciences. (1976). Respiration of amphibious vertebrates. London: Academic Press.
Perry, S. F., & Tufts, B. L. (1998). Fish respiration. San Diego, Calif: Academic Press.