Aim:
To see how different concentrations of caffeine affect the hear rate of daphnia.
We used concentrations: 0, 0.001, 0.01, 0.1, 1, 10, 100 percent.
Equipment:
To see how different concentrations of caffeine affect the hear rate of daphnia.
We used concentrations: 0, 0.001, 0.01, 0.1, 1, 10, 100 percent.
Equipment:
- petri dishes
- microscope
- cotton wool
- pipettes
- caffeine of different concentrations
- daphnia
- size of daphnia= larger daphnia would have a higher metabolic rate and thus a higher heart rate
- temperature= the lamp from the microscope could cause the daphnia to have a higher metabolic rate due to enzyme controlled reactions and thus a higher heart rate in order to supply sufficient levels of oxygen and remove carbon dioxide. to minimise this factor we observed the daphnia quickly and ensured we kept them under constant room temperature conditions outside of the microscope.
Preparation
a Take a small piece of cotton wool, tease it out and place it in the middle of a small Petri dish.
b Select a large Daphnia and use a pipette to transfer it onto the cotton wool fibres.
c Immediately add pond water to the Petri dish until the animal is just covered by the water.
d Place the Petri dish on the stage of a microscope and observe the animal under low power. The beating heart is located on the dorsal side just above the gut and in front of the brood pouch (see diagram). Make sure that you are counting the heart beats, and not the flapping of the gills or movements of the gut. The heart must be observed with transmitted light if it is to be properly visible.
e Use a stopwatch to time 20 seconds, and count the number of heart beats in several periods of 20 seconds. The heart beat of Daphnia is very rapid, so count the beats by making dots on a piece of paper in the shape of a letter S. Count the dots and express heart rate as number of beats per minute.
f At the end of the investigation, return the Daphnia to the stock culture.
repeat method for different concentrations of caffeine.
a Take a small piece of cotton wool, tease it out and place it in the middle of a small Petri dish.
b Select a large Daphnia and use a pipette to transfer it onto the cotton wool fibres.
c Immediately add pond water to the Petri dish until the animal is just covered by the water.
d Place the Petri dish on the stage of a microscope and observe the animal under low power. The beating heart is located on the dorsal side just above the gut and in front of the brood pouch (see diagram). Make sure that you are counting the heart beats, and not the flapping of the gills or movements of the gut. The heart must be observed with transmitted light if it is to be properly visible.
e Use a stopwatch to time 20 seconds, and count the number of heart beats in several periods of 20 seconds. The heart beat of Daphnia is very rapid, so count the beats by making dots on a piece of paper in the shape of a letter S. Count the dots and express heart rate as number of beats per minute.
f At the end of the investigation, return the Daphnia to the stock culture.
repeat method for different concentrations of caffeine.