Edexcel A-Level Biology A 9BN0
Lifestyle, Health and Risk
Genes and Health
Voice of the Genome
Biodiversity and Natural Resources
On the Wild Side
Immunity, Infection and Forensics
Run for Your Life
Grey Matter
Lifestyle, Health and Risk
Core practical: caffeine and the heart rate of Daphnia
- 3 things to know
- Papers 1, 2 and 3
Overview
Recall questions on preparing Daphnia, the variables in the investigation, and the ethical considerations of using invertebrates.
What you need to know
Answer each one before you reveal it.
What is the independent variable when investigating caffeine's effect on Daphnia heart rate?
State four controlled variables in the Daphnia caffeine experiment.
Questions from this subtopic
Each one with the model answer underneath.
- 1
How are Daphnia prepared for observation when investigating caffeine's effect on heart rate?
Model answer
Daphnia are placed in pond water on a cavity slide under a microscope.
- 2
How is heart rate measured in Daphnia?
Model answer
By observing the beating heart through the transparent body wall and counting beats over a set time period.
- 3
What is the independent variable when investigating caffeine's effect on Daphnia heart rate?
Model answer
Different concentrations of caffeine solution.
- 4
State four controlled variables in the Daphnia caffeine experiment.
Model answer
Temperature, size of Daphnia, volume of solution, and acclimatisation time.
- 5
Why must temperature be controlled in the Daphnia heart rate experiment?
Model answer
Because metabolic rate and heart rate are affected by temperature changes.
- 6
What ethical issue relates to whether invertebrates should be used in research?
Model answer
Whether invertebrates can experience pain or distress.
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