Problem
Factors Influencing Daphnia Heartrate
Daphnia is a tiny crustacean (related to shrimp) with a transparent outside skeleton (carapace) and joined legs. Like other arthropods, its heart is on its back and it is a conformer.
Chemicals that enter their bodies can change their heart rate by interfering with the chemicals that nerves use to transmit signals. Chemicals that speed up heart rate are known as stimulants, whereas chemicals that slow down heart rate are known as depressants.
Hypothesis Question: How will each of your chemicals affect the Daphnia heart rate?
Lab Results :
(New Daphnia for every trial)
Group A : Caffine 20 mg x spring water
Daphnia 1 - Regular heart rate - 17 x 6 = 102 Bpm
Trial #1: 2 drops caffeine (20mg) , 4 drops spring water
Trial results: 23 x 6 = 138 Bpm (2%)
Daphnia 2 - Regular heart rate - 29 x 6 = 174 Bpm
Trial #2: 4 drops caffeine (20mg) , 6 drops spring water
Trial results: 18 x 6 = 108 Bpm (4%)
Daphnia 3 - Regular heart rate - 23 x 6 = 138 Bpm
Trial #3: 6 drops caffeine (20mg) , 8 drops spring water
Trial results: 13 x 6 = 78 Bpm (3%)
Group B: 1 mg/ml of dextromethorphan x spring water
Daphnia 1 - Regular heart rate - 16 x 6 = 96 Bpm
Trial #1: 1 drop Dextromethorphan , 2 drops spring water
Trial results: 15 x 6 = 90 Bpm (1%)
Daphnia 2 - Regular heart rate - 17 x 6 = 102 Bpm
Trial #2: 2 drops Dextromethorphan , 4 drops spring water
Trial results: 18 x 6 = 108 Bpm (2%)
Daphnia 3 - Regular heart rate - 19 x 6 = 114 Bpm
Trial #3: 3 drops Dextromethorphan , 6 drops spring water
Trial results: 22 x 6 = 132 Bpm (3%)
This problem requires the following questions
Analysis:
i. Graph your BPM data for each chemical on one graph.
ii. Interpret your data in a quantifiable manner (rate of change).
iii. For the Daphnia, does your variable act a stimulant, a depressant or neither?
iv. What effects do your variables have on the human brain, heart, rest of the body?