Laboratory 10 Alternate: Respiration Rate and Temperature AKA The Goldfish Lab!

Transcription

1 Laboratory 10 Alternate: Respiration Rate and Temperature AKA The Goldfish Lab! Introduction: Ectothermic animals do not maintain a constant body temperature; their body temperature tends to be near that of the environment. In these animals, the metabolic rate, which is affected by temperature, varies over a wide range. In ectothermic animals, there is a direct relationship between the rate of many physiological activities and environmental temperature. The rate of metabolism in these animals increases as environmental temperatures increase from approximately 5 C to 35 C. Increasing the temperature by 10 C results in an approximate doubling of the metabolic rate. That is why a snake or lizard can hardly move when it is cold but becomes quite active after warming in the sun. In fishes, the exchange of respiratory gases occurs as water flows across the gills. The rate of oxygen uptake can be measured indirectly by observing the rate at which the operculum, or gill flap, or the mouth opens and closes. Changes in environmental temperature should affect the rate of respiration in a fish. Materials: Medium-Sized Goldfish Thermometer Hotplate Crushed Ice Pipettes Stopwatch Small fish net Two Large Beakers (1000 ml) Procedure: You will be placing your fish into water of 4 different temperatures, beginning with the warmest. The temperatures will be approximately 25 C, 20 C, 15 C, and 10 C. These temperature values are arbitrary. Do not spend valuable time attempting to get these exact temperatures. Simply record the exact temperature at which each respiratory rate is determined. While your fish is acclimating to one temperature of water, you will be preparing a second beaker. Go to the analysis section of this lab. Record your hypothesis about the effects of various temperatures on the respiration rate of a fish there. 1. Fill a 1000 ml beaker ab0ut two-thirds full with aquarium water at room temperature. Measure and record the temperature of the water. 2. Fill another 1000 ml beaker with slightly less water than the first, and then add heated water to this beaker to raise its temperature approximately 5 C above the first beaker. 3. Place a goldfish in the second (warm) beaker. Allow the fish to acclimate for 3 minutes. During this time make two practice counts of mouth or opercular openings per fifteen seconds. You will use this to determine the respiration rate

2 4. Count the number of times the fish opens and closes its mouth or operculum in 15 seconds. Repeat for a total of three measurements. Calculate the average respiration rate per minute. 5. Carefully move your fish to the beaker with room temperature water. Record the water temperature. While you are waiting for the fish to acclimate to the new beaker, add ice chips to the warm beaker until its water temperature is 5 C below the room temperature beaker. Repeat the counting procedure. 6. Move the goldfish to the cooler beaker. While you are waiting for the fish to acclimate to the new beaker, add ice chips to the room temperature beaker until its water temperature is about 10 C below room temperature. Repeat the counting procedure. (You should now have data for 5 C above room temperature, room temperature, 5 C below room temperature and 10 C below room temperature.) 7. At the conclusion of your data collection, gradually add some warm water to the final beaker to bring its temperature to the approximate temperature of the aquarium. Return the fish to the aquarium and recycle the aquarium water. 8. Graph temperature versus average respiration rate (respirations/min). Data Table: Temperature Respirations/15 sec Trial Average Respirations/min (Warm) (Room) (Cold) (Very Cold) Analysis: 1. Formulate a hypothesis about the affects of various temperatures on the respiratory rate of a fish

3 2. What kind of pattern is evident from your graph? Do the data in the graph support or refute your hypothesis? 3. Why does temperature affect respiration rate in ectotherms? 4. At what temperature does your graph indicate that the fish s respiratory rate would equal zero? 5. Why is it important to wait a few minutes after placing your fish in the new temperature water before counting the respiratory rate? 6. What is the experimental advantage of starting with the warmest temperature and working gradually in the other direction, instead of skipping around to different temperatures? 7. How would you expect temperature to affect the fish s need for food and oxygen? On what do you base your assumptions? - 3 -

4 8. What happens to the activity of fishes in cold climates during the winter months? 9. What do you think is the effect of environmental temperature on the metabolic rate of a homoiotherm, such as man, within a comfortable range of temperatures that is neither near freezing nor very hot? Why? 10. How might an ectothermic organism s behavior help it regulate its temperature? Give at least 3 specific examples

5 The independent variable: Use this to label the horizontal (x) axis. The dependent variable: Use this to label the vertical (y) axis. Title: - 5 -