other arthropods, its heart is on its back. Air, water, heat, and light challenge are bodies every

Transcription

1 Daphnia Anatomy Background Information A Daphnia is a tiny crustacean that has a clear outside skeleton and jointed legs. Like other arthropods, its heart is on its back. Air, water, heat, and light challenge are bodies every day to react to their effects. Because Daphnia are ectotherms, their body temperature changes with the surrounding environment. Since chemical reactions speed up in warmer temperatures, what would you predict the effect of temperature changes would be on their rate of metabolism (and heart rate)? Chemicals which enter their bodies can also change their heart rate by nterfering with the chemicals that nerves use to transmit signals. Chemicals that speed up heart rate are known as stimulants, whereas chemicals that slow down the heart rate are known as depressants. Given an ethanol solution and a caffeine solution make a prediction. Hypothesis MATERIALS Digital Microscope Personal Computer Living Algae (chlamydomonas) Living Daphnia Depression Slides Ethanol Caffeine Tablets, Coffee, or Tea Transfer Pipettes 1

2 PROCEDURE Activity 1 1. Observe any changes occurring in the aquarium on the live feed set up by your teacher on the Interactive White Board (IWB). 2. Obtain a Daphnia sample from the aquarium using a clean pipette. 3. Place one Daphnia on a clean depression slide WITHOUT a cover slip with one drop of water. Keep the drop small so the Daphnia can t swim out of your field of view! 4. Place the slide under the digital microscope. 5. Observe, record, and label the various parts of the Daphnia using 2x, 4x, and 10x magnification. 6. Return Daphnia to aquarium. 7. Answer Activity 1 questions in your science notebook. Activity 2 1. Observe any changes occurring in the aquarium on the live feed set up by your teacher on the Interactive White Board (IWB). 2. Obtain a Daphnia sample from the aquarium using a clean pipette. 8. Place one Daphnia on a clean depression slide WITHOUT a coverslip with one drop of water. Keep the drop small so the Daphnia can t swim out of your field of view! 3. Review and find the various parts of the Daphnia, which you labeled in Activity Find the heart. 5. Count the rate of its heartbeat for 10 seconds. a. To do this, record a movie for 10 seconds, then go back and review the movie to count how many heartbeats occurred. 6. Multiply this rate by 6 to give the rate of the heartbeat for one minute. 7. Record in Data Table Part B. 8. Repeat steps 4-7, with a drop of caffeine solution to the same Daphnia. 9. Repeat steps 4-7 with a drop of diluted ethanol to the same Daphnia. 10. Draw and label the Daphnia for any changes observed in the control solution, the caffeine solution, and the ice water solution. 2

3 11. Answer Activity 2 questions in your science notebook. Activity 3 1. Observe any changes occurring in the aquarium on the live feed set up by your teacher on the Interactive White Board (IWB). 2. Watch very carefully as your teacher introduces the fish back into the aquarium. 3. Record what you observe and make inferences in your science notebook. 4. Answer Activity 3 questions in your science notebook and start working on your presentation. QUESTIONS Activity 1 1. Why is the Daphnia often green? 2. What is the purpose of the legs on the Daphnia? 3. Draw a diagram of a food web in which organisms such as Daphnia would be involved. 4. Is Daphnia classified as autotrophic or heterotrophic? 3

4 5. What type of organism would most likely feed on the Daphnia? Why? Activity 2 Dependent Variables (DV): Independent Variable (IV): Predict the effect of the IV on the DV: Control Caffeine Ethanol 4

5 Data Table 1 Trial 1 Trial 2 Trial 3 Average Accept Data (Yes or No) Water Caffeine Ethanol 10 sec. BPM (x6) 10 sec. BPM (x6) 10 sec. BPM (x6) 1. How do various chemicals affect the heart rate of a Daphnia a. in water? b. in a caffeine solution? c. in an ethanol solution? 2. When you add a drop of caffeine solution did it increase or decrease the heart rate? 3. When you add a drop of ethanol solution did it increase or decrease the heart rate? 4. Did the data support your hypothesis? (Yes or No) Why? 5. Would you classify caffeine as a stimulant or a depressant? 6. Would you classify ethanol as a stimulant or a depressant? 5

6 Activity 3 1. Construct a food web based on observations of Day How would these organisms of algae, daphnia, and fish relate to a mountain lion in the natural environment? 3. How would drought affect their relationships? 4. How would water pollution affect their relationships with you? 6