Design an experiment that students can perform to verify the prediction coffee will increase heart rate in daphnia?

Hypothesis:

If caffeine increases the heart rate of Daphnia, then the heart rate of Daphnia exposed to coffee will be higher than the heart rate of Daphnia exposed to water.

Materials:

* 24 Daphnia (water fleas)

* 2 beakers (at least 100 mL) with lids

* Coffee (instant or ground coffee diluted to a concentration of 0-5%)

* Pipette

* Microscope

* Stopwatch

Procedure:

Collect Daphnia

1. Label the beakers "Coffee" and "Water".

2. Fill each beaker with 100 mL of water.

3. Add 1 mL of instant coffee or ground coffee diluted to a concentration of 0-5% per 100 mL of water in the "Coffee" beaker.

4. Transfer twelve Daphnia to each beaker using a pipette.

5. Put the lids on the beakers to prevent the Daphnia from escaping.

Observe Daphnia Heart Rate

1. Observe the Daphnia under the microscope at 40x magnification.

2. Locate the heart of the Daphnia. The heart will be the only structure pulsating in the thoracic region.

3. Count the number of times the heart beats over 30 seconds and record the data in Table 1 below.

Table 1: Daphnia Heart Rate in Coffee and Water Treatments

Treatment | Daphnia 1 | Daphnia 2 | Daphnia 3 | Daphnia 4 | Daphnia 5 | Daphnia 6 |

--------- | -------- | -------- | -------- | -------- | -------- | -------- |

Coffee | | | | | | |

Water | | | | | | |

Repeat Steps 6-8 for each of the Daphnia in both the "Coffee" and "Water" beakers.

Data Analysis:

1. Calculate the average heart rate for each treatment group by adding the heart rates of all the Daphnia in the group and dividing that number by the total number of Daphnia.

2. Compare the average heart rates of the two treatment groups.

Expected Results:

The average heart rate of the Daphnia in the "Coffee" group will be higher than the average heart rate of the Daphnia in the "Water" group indicating that coffee increases the heart rate in daphnia.

Conclusion:

Based on the results of this experiment, we accept the hypothesis that caffeine increases the heart rate of Daphnia.