Monai Elnaasani
Describe how the effect of caffeine on heart rate in Daphnia can be
investigated practically, and discuss whether there are ethical issues in the
use of invertebrates.
Past paper - June 2012, June 2016
1. Collect daphnia of same size, age, species and gender
2. Place cotton wool strings in a cavity slide
3. Take daphnia in a pipette with water
4. Place a drop of water along with daphnia in a cavity slide
5. Focus the microscope on the heart of the daphnia
6. Count the number of heart beat in 30 seconds by marking dots on a white paper
with pencil
7. Repeat the counting
8. Prepare solutions of caffeine of different concentration, 0.5%, 1%, 1.5%, 2%,
2.5%
9. Place a drop of caffeine solution in the cavity slide along with a daphnia
10. Allow daphnia to acclimates for 5 minutes
11. Record the heart beat
12. Repeat the steps and calculate the mean
13. Repeat with other concentrations
14. Collect data, draw graph
Independent variable;
• Caffeine concentration
Dependent variable;
• Heart rate of daphnia
Variables to control;
• Temperature; heat shield
• Volume of caffeine solution, use pipette to measure stated volume
• Age, gender, species of daphnia, eggs hatched same time
• Same acclimatisation time
• Reduce movement of daphnia by using cotton wool strands
• Count number of heartbeats in 30 seconds
• Concentration of caffeine
• Dissolved oxygen by bubbling air
• pH using buffer
Why use a Daphnia;
• Less developed nervous system
• Transparent
• Less ethical concert because it’s an invertebrate
• Can absorb chemicals from surrounding solution quickly
• Cheap and abundant and used as fish food
• Easy to manipulate
Pearson Edexcel Advanced Level Biology Unit 3 - notes for success
Describe how the effect of caffeine on heart rate in Daphnia can be
investigated practically, and discuss whether there are ethical issues in the
use of invertebrates.
Past paper - June 2012, June 2016
1. Collect daphnia of same size, age, species and gender
2. Place cotton wool strings in a cavity slide
3. Take daphnia in a pipette with water
4. Place a drop of water along with daphnia in a cavity slide
5. Focus the microscope on the heart of the daphnia
6. Count the number of heart beat in 30 seconds by marking dots on a white paper
with pencil
7. Repeat the counting
8. Prepare solutions of caffeine of different concentration, 0.5%, 1%, 1.5%, 2%,
2.5%
9. Place a drop of caffeine solution in the cavity slide along with a daphnia
10. Allow daphnia to acclimates for 5 minutes
11. Record the heart beat
12. Repeat the steps and calculate the mean
13. Repeat with other concentrations
14. Collect data, draw graph
Independent variable;
• Caffeine concentration
Dependent variable;
• Heart rate of daphnia
Variables to control;
• Temperature; heat shield
• Volume of caffeine solution, use pipette to measure stated volume
• Age, gender, species of daphnia, eggs hatched same time
• Same acclimatisation time
• Reduce movement of daphnia by using cotton wool strands
• Count number of heartbeats in 30 seconds
• Concentration of caffeine
• Dissolved oxygen by bubbling air
• pH using buffer
Why use a Daphnia;
• Less developed nervous system
• Transparent
• Less ethical concert because it’s an invertebrate
• Can absorb chemicals from surrounding solution quickly
• Cheap and abundant and used as fish food
• Easy to manipulate
Pearson Edexcel Advanced Level Biology Unit 3 - notes for success
