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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.

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Key term

How are Daphnia prepared for observation when investigating caffeine's effect on heart rate?

Key term

What is the independent variable when investigating caffeine's effect on Daphnia heart rate?

Key term

State four controlled variables in the Daphnia caffeine experiment.

Questions from this subtopic

Each one with the model answer underneath.

  1. 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. 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. 3

    What is the independent variable when investigating caffeine's effect on Daphnia heart rate?

    Model answer

    Different concentrations of caffeine solution.

  4. 4

    State four controlled variables in the Daphnia caffeine experiment.

    Model answer

    Temperature, size of Daphnia, volume of solution, and acclimatisation time.

  5. 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. 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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