BREATHING RATE IN FISH Introduction Animals must have oxygen to survive. The lungs of land animals remove oxygen from the air. Aquatic animals get their oxygen from the water in which they live. The oxygen in water does not come from oxygen molecules in H20. Instead, oxygen in aquatic habitats is oxygen gas, 02, which is dissolved in water. Gills, shown in Figure 1, are the organs in fish that take up oxygen. When water flows over gills, oxygen diffuses into the blood vessels. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. When fish are active, they need more oxygen than they do when they are resting. Other factors also affect their need for oxygen. In this experiment, you will measure the respiration rate of a fish and find out how temperature affects this rate.

gills

Figure 1

Figure 1

Time Needed 55 minutes

What You Need

F 1 guppy or goldfish F small dip net © Infobase Publishing

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F small, transparent glass container with water F floating aquarium thermometer F hot plate F 100-ml beaker F ice F stopwatch F access to dechlorinated water F science notebook

(300-milliliter [ml] beaker or pint jar)

Safety Precautions Handle guppies with care, touching them as little as possible. After working with guppies, wash your hands with soap and water. Please review and follow the safety guidelines.

What You Do 1. Fill your small, transparent glass container with dechlorinated water. Use the dip net to collect one guppy from the aquarium and place it in your container, as shown in Figure 2. Be sure there is enough water in the container to completely cover the fish.

dip net

aquarium

Figure 2 Figure 2

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Place a floating aquarium thermometer in the center of the container with the goldfish. Let the thermometer stand in the container for 2 or 3 minutes, then record the temperature on Data Table 1, beneath “Room temperature water.” To find the respiration rate of the fish, count the number of times the fish opens and closes its gills in 1 minute. Record the respiration rate on Data Table 1 in the column labeled “Trial 1.” Repeat step 3 two more times and record your findings on Data Table 1 in the columns labeled “Trial 2” and “Trial 3.” Find the average rate of respiration for all three trials. Record the average in the last column of Data Table 1. Place two or three ice cubes in the container with the fish. After a few minutes, check the water temperature and record it on Data Table 2, beneath “Cold water.” Repeat the procedure in steps 3 to 5. Record all results on Data Table 2. Remove the ice cubes from the container of water. Place 70 ml of dechlorinated water in a 100-ml beaker. Put the beaker on the hot plate and set the thermostat on medium. Every minute or two, check the temperature by gently swirling the thermometer bulb in the water. Continue to heat the water until it reaches about 80°C (176°F). While the water is heating on the hot plate, remove some of the water in the fish container until there is only enough to completely cover the fish. Slowly add about 10 ml of the warm water to the fish container. Measure the temperature of the water in the fish container. Repeat this process until the temperature of the water is about 50°C (122°F). Record the temperature on Data Table 3, beneath “Warm water.” Repeat the procedure in steps 3 to 5. Record all results on Data Table 3. Gently return the goldfish to the aquarium following your teacher’s instructions.

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Data Table 1: Respiration rates in room temperature water Respiration rates Room temperature water

Trial 1

Trial 2

Trial 3

Average rate of respiration

Data Table 2: Respiration rates in cold water Respiration rates Cold water

Trial 1

Trial 2

Trial 3

Average rate of respiration

Data Table 3: Respiration rates in warm water Respiration rates Warm water

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Trial 1

Trial 2

Trial 3

Average rate of respiration

BREATHING RATE IN FISH

Observations 1. How does temperature affect the rate of respiration in a guppy? 2. Would a fish exert more energy to breathe in colder or warmer waters? Explain. 3. What other factors do you think might affect the respiration rate of a fish?

Want to Know More? See Our Findings.

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SAFETY PRECAUTIONS Review Before Starting Any Experiment GENERAL • Always obtain your teacher’s permission for experiments performed at school, and your parent’s permission for experiments performed at home, before attempting any experiment. • Read all instructions for an experiment before starting the experiment, and follow the directions exactly as they appear in this volume. • If an experiment requires adult supervision, do not perform the experiment unless you have an adult supervising you the entire time you are performing the experiment. • Wash your hands before the start of and after each experiment you perform. • Keep your work area clean. • Never eat or drink while performing an experiment. Never taste a substance used in an experiment unless you are told that it is safe to do so. • Be aware of the location of safety equipment you may need in an emergency, such as running water, an eyewash if you are at school, and a fire extinguisher. • If you are going outside, make sure you have permission to go from your teacher and parent. Take a buddy with you, and dress appropriately for the weather. Make sure you or someone who accompanies you is familiar with the area, and bring along a firstaid kit in case of emergency. • Never look directly into the Sun. CHEMICAL SAFETY • Always wear goggles when working with chemicals, such as acids and bases, and near heat sources like flames. If at all possible, avoid wearing contact lenses when working with chemicals. • If any substance gets into your eyes, notify an adult (e.g., your teacher or parent) immediately, and flush your eyes with running

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water for at least 15 minutes. Do not mix chemicals unless you are told to do so by a teacher or parent. • Never touch, taste, or smell chemicals unless instructed to do so. • Keep chemicals in closed containers when they are not in use. • Dispose of all chemicals properly. Do not pour any chemicals or solids down the drain unless instructed to do so. • Use safety gloves and a plastic apron when handling chemicals. If any chemicals spill on your skin, rinse the affected area with running water for at least 10 minutes, and notify your teacher or parent immediately. • Take precautions to avoid spilling chemicals. If a chemical spills on any surface, notify your teacher or parent immediately to assist with clean-up. • Exercise caution when using sharp instruments such as knives or scissors. Always cut away from yourself, not toward yourself. If you cut yourself, notify your teacher or parent immediately. GLASSWARE • Clean glassware when you are finished with the experiment. • Be careful when using glassware. If a piece of glassware breaks, have an adult assist you in clean-up to avoid injuries from broken glass. Never use broken or damaged glassware. FIRE SAFETY • Do not heat glassware that is not completely dry. Do not pick up hot glassware without heat-resistant gloves or tongs. • When heating glassware, keep it away from yourself and from others. • Do not heat anything unless instructed to do so by a teacher or parent. • Do not heat substances in a closed container. • After an experiment, make sure that all heating sources are off and that all flames have been put out.

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• Do not reach across such heating sources as flames. • If you have long hair, tie it back, out of the way. Do not wear clothing with loose sleeves, scarves, bows, ties, or anything else that may hang into a fire. Do not wear long earrings. ELECTRICAL SAFETY • Do not touch electrical equipment when your hands are wet. • Do not plug several electrical devices into one outlet or use an extension cord.

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