Learn: Core Practical 1 - Caffeine and Daphnia Heart Rate

Welcome!Today we'll explore how caffeine affects the heart rate of Daphnia. This practical helps us understand the biological impact of stimulants on organisms. Let's dive in!

What is caffeine?Caffeine is a stimulant found in coffee, tea, and energy drinks. It increases alertness and affects the nervous and cardiovascular systems. Understanding its effects helps us study how stimulants interact with living organisms.

Why use Daphnia?Daphnia are small freshwater invertebrates whose heart rate can be easily observed under a microscope. They are sensitive to environmental changes, making them ideal for studying the effects of chemicals like caffeine.

Setting up the practicalTo investigate, you'll place Daphnia in a small water droplet on a slide. Gradually introduce caffeine solutions of different concentrations and observe how their heart rate changes. Accurate measurement and ethical considerations are key.

Ethical considerationsWhen using living organisms like Daphnia, minimise harm. Avoid prolonged exposure to caffeine and ensure they are returned to their environment after the experiment. Handling them gently is important.

Measuring heart rateTo measure heart rate, count the number of beats in a set time period (e.g., 15 seconds) and multiply to get beats per minute. Repeat for different caffeine concentrations to observe trends.

Recording resultsRecord heart rates for each caffeine concentration in a table. Ensure accuracy by repeating measurements and calculating the average. This helps identify reliable patterns.

Analysing dataPlot a graph with caffeine concentration on the x-axis and heart rate on the y-axis. Look for trends: does heart rate increase with higher caffeine levels? Consider biological reasons for these changes.

Review Time!Great work! You've learned about caffeine, Daphnia, setting up the practical, ethical considerations, and analysing results. Now let's test your understanding with a few questions.