Learn: Core Practical 1 – Caffeine and Daphnia Heart Rate

Welcome!You've already learned about the cardiovascular system and factors affecting heart rate. Today, we'll explore how caffeine affects heart rate using Daphnia, a small aquatic organism. This builds on your understanding of heart function and experimental techniques.

Why study Daphnia?Daphnia are small invertebrates often used in experiments because their heart is visible under a microscope. Studying their heart rate helps us understand how substances like caffeine affect physiology without using more complex animals.

What is caffeine?Caffeine is a stimulant that increases alertness by affecting the nervous system. It can speed up heart rate, which is why it's often studied in biology. Understanding its effects on heart rate gives insight into how stimulants work.

Experimental setupTo study the effect of caffeine on Daphnia heart rate, you will prepare slides with live Daphnia, add caffeine solutions of varying concentrations, and count heartbeats under a microscope.

Key Procedure1. Place a live Daphnia on a slide with a few drops of water.2. Add a caffeine solution of known concentration.3. Observe the heart under the microscope and count beats for 10 seconds.4. Repeat with different caffeine concentrations.

Variables in the experimentExperiments have three types of variables:Independent variable: Concentration of caffeine.Dependent variable: Heart rate of Daphnia.Control variables: Temperature, volume of solution, time observed.

Ethical considerationsUsing live organisms like Daphnia raises ethical questions. It's important to minimise harm by limiting exposure to high caffeine concentrations and returning Daphnia to their habitat after the experiment.

Review Time!Great work! You've learned about Daphnia, caffeine, experimental setup, variables, and ethical considerations. Let's test your knowledge.