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Learn: Core Practical 1 - Caffeine and Daphnia Heart Rate
Edexcel A Level Biology SNAB A
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Welcome!Welcome to Core Practical 1: Investigating the effect of caffeine on heart rate in Daphnia. Building on what you've learned about the cardiovascular system and blood pressure, this practical will help you understand how external substances can influence heart rate.
Why Daphnia?Daphnia are small freshwater invertebrates often used in experiments due to their transparent bodies which allow observation of the heart. They are ideal for investigating factors affecting heart rate in a controlled way.
Caffeine's EffectCaffeine is a stimulant that can increase the heart rate. In humans, it affects the central nervous system, but in Daphnia, its direct effect on the heart rate can be observed easily by counting heartbeats under a microscope.
Caffeine is classified as a {{blank0}} which can {{blank1}} heart rate.
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Ethical ConsiderationsUsing Daphnia raises ethical concerns. Although they are small and simple organisms, ensuring their wellbeing by minimising harm during experiments is important. For example, avoid prolonged exposure to caffeine or excessive handling.
Which ethical principle should you follow when using Daphnia?
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How to Perform the PracticalTo investigate caffeine's effect on Daphnia heart rate, follow these steps:Place a Daphnia in a drop of water on a microscope slide.Add a small amount of caffeine solution to the water.Observe and count heartbeats using a microscope for a set time period.Repeat with different caffeine concentrations to compare results.
Which of the following steps are part of this practical? (Select all that apply)
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Variables to ControlIt's crucial to control variables for reliable results. Keep temperature, Daphnia size, and observation time constant while varying only caffeine concentration.
Match the items on the left with their correct pairs on the right
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Review Time!Great work! You've learned about caffeine's effects on Daphnia, ethical considerations, and how to perform the practical. Now let's test your understanding with a few questions.
Why are Daphnia used for this practical?
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Which variables must be controlled during the practical? (Select all that apply)
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The {{blank0}} variable is the caffeine concentration, while the {{blank1}} variable is the Daphnia heart rate.
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