Daphnia Practical

Question 1

Describe method for effect of caffeine on heart rate of daphnia

Answer 1

1. Dilute the caffeine solution with distilled water to produce several different concentrations.
2. Place some cotton wool (to restrict movement) on a cavity slide. Add one large water flea.
3. Use filter paper to absorb the water around the flea.
4. Then use a dropping pipette to add a few drops of distilled water to the slide.
   Do not use a coverslip to prevent conditions from becoming anoxic.
5. Use a stop clock to time a minute and record the number of heartbeats.
6. Repeat the experiment, replacing the distilled water with a caffeine solution.

Question 2

Why does caffeine increase heart rate?

Answer 2

It is a stimulant, releases excitatory neurotransmitters

Question 3

Why are Daphnia used in this practical?

Answer 3

Because they have a translucent body making the heartbeat easy to observe to count heart rate