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The Effect of Caffeine on the Heart Rate of Daphnia Magna

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Author: Shumit DasGupta
Type

Life Science 

Grade Level

Late Middle/High school 

Difficulty of Project

Medium

Cost

Live Daphnia cultures can be ordered online for anywhere from $3-$30, or be purchased from your local fish store. Live yeast can be used as food, for $2 a packet. Distilled water- or tap water left out for 48 hours- is also inexpensive. While laboratory grade caffeine is both expensive and dangerous, any household chemical can be used cheaply- coffee works just fine, as does any household food product or chemical that might have an effect on heart rate.

TOTAL: $10-50.
Safety Issues

Care should be taken when mixing solutions. All safety hazards and guidelines that apply to any chemicals used should be followed. 

Material Availability 

Almost all high school labs will have access to microscopes, well slides and the appropriate glassware. Daphia must be purchased from an aquarium or online, and it’s a good idea to start a living culture, which is easy enough. Any other supplies can be purchased at any grocery store 

Approximate Time Required to Complete the Project  

Gathering the materials is the lion’s share of the work- plan on a week to receive the daphnia in the mail hour to set up a culture, and an hour to make solutions. After this, data collection is fairly quick- you could gather a reasonable amount of data in three 30-minute sessions (or one 90-minute microscope marathon) and be done. 

Objective 

What is the project about?

Daphnia, otherwise known as water fleas, have a circulatory system similar to mammals. Most importantly, they have a chambered heart, which can be seen beating under a microscope. With a stopwatch and attention to detail, you can test whether a particular chemical has any effect on heart rate. 

What are the goals?

To determine if a particular chemical has an effect (increase or decrease) on the heart rate of Daphnia. 

Materials and Equipment / Ingredients 

What materials are required? 
  • Daphnia (water fleas)
  • Jar or other glass container and distilled water to make a habitat.
  • Bread yeast ( daphnia food)
  • Compound light microscope
  • Deep well microscope slides
  • Graduated cylinder
  • Graduated pipette/disposable pipettes
  • Stopwatch
  • Distilled water ( 1-2 gallons) or tap water left with open air for 48 hours
  • Chemical of your choice ( coffee, caffeine, weed killer, sports drinks, etc.)
Where can the materials be found? 
  • Aquarium store or online (site listed below)
  • Any large household jar- distilled water at the grocery.
  • Grocery store
  • High school science lab ( ask your science teacher)
  • Grocery or tap.
  • Grocery 

Introduction 

Background information 

Daphnia, otherwise known as water fleas, have a circulatory system similar to mammals. Most importantly, they have a chambered heart, which can be seen beating under a microscope. With a stopwatch and attention to detail, you can test whether a particular chemical has any effect on heart rate. 

Their hearts are found on their dorsal side ( their ‘backs’), above the brood pouch where you may find young if the Daphnia is a female. You can see a diagram of a typical Daphnia at this website: http://webs.lander.edu/rsfox/invertebrates/daphnia.html 

The heart can easily be seen beating- the only thing it might be confused with is/are young of the Daphnia, as they are moving as well, but not in as regular of a pattern. 

We can dilute certain chemicals and apply them to Daphnia, and watch to see if the heart rate changes! 

Any required diagrams/pictures (Pictures speak a thousand words!) 
See above link.  
Research Questions
  • What is a closed circulatory system?
  • How are Daphnia hearts like mammalian hearts?
  • How do chemicals affect heart rate? ( focus on your target chemical) 
Terms, Concepts and Questions to Start Background Research

Closed circulatory system, chambered heart, heart rate, caffeine (or other target chemical).

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