Applied Science Level 3 Unit 6 Investigative Project Learning Aim C&D

Learning aim D: review the investigate project using correct scientific principles

Project implementation and review

Investigating factors affecting the heart rate of daphnia

Abstract

The experiment is about the effect of several concentration of caffeine on the heart rate of daphnia.
Caffeine is a natural stimulant commonly found in tea, coffee, and cocoa plants and works by
stimulating the brain and central nervous system and as well prevent the onset of tiredness. Caffeine
works by blocking the effects of adenosine- a neurotransmitter that relaxes the brain and makes you
get tired. The reason for the investigation is to find out how caffeine affects the heart rate of
daphnia. To get the experiment perfect, several concentrations of caffeine were given. The reason
for using daphnia is because its heart combines with that of humans.

Introduction

Daphnia are small planktonic crustaceans under arthropoda phylum and they are tiny compared to
crabs, lobster, crayfish and shrimp and daphnia are aquatic organisms. Daphnia is an interesting
organism and a good model organism for scientific studies and are also great interest to ecologist
and geneticists. Daphnia are good comparative genomic studies among arthropods. The unusual life
cycle of the daphnia has been under investigation for more than a century for cyclic pathogenesis. It
can produce diploid and haploid eggs. Daphnia has a myogenic heart that is like the heart of a
human and daphnia has a transparent body that allows the heartbeat to be seen clearly. An
experimental result has showed that daphnia gained protection from fungal parasites through the
toxins that were present in bloom-forming cyanobacteria.

Daphnia synthesise secondary metabolites that might have antimicrobial properties and daphnia
mature fully within few days of birth and cannot be used for experiment if they are not close to
extinction. Most of other daphnia have only 20 chromosomes, both sex of daphnia can be used for
the experiment if a female dies during the experiment a male daphnia can be used.

Aim: To investigate the effect of caffeine on the heart rate of daphnia

Hypothesis: The experiment is to see how caffeine affects the heart rate of daphnia. The higher the
concentration of caffeine the higher the heart rate pf daphnia.

Dependent variable:

 Heart rate of daphnia

Independent variable:

 Concentration of caffeine

Control variable:

 Size of daphnia
 Volume of solutions
 Time
 The temperature of the water
 The light intensity of the microscope

Equipment

,  Microscope
 Cotton wool
 Pipette
 Daphnia
 Paper towel
 Cavity slide
 Test tubes
 Stopwatch
 Caffeine solution

Method

 Place a cotton wool on the cavity slides and put it under the microscope
 Use a pipette to take a daphnia from a water pond and put it on the cavity slide and use a
paper towel to drain the water around the daphnia
 Add 1-2 drops of caffeine solution to the daphnia with a pipette
 Leave the daphnia for some seconds to show the effect of caffeine
 Turn on the microscope and position the cavity slide properly to see the heartbeat of the
daphnia
 Use a stopwatch to count the heartbeat between 1-5minutes and write down the number of
heart beat on a table
 Repeat the process using different concentrations of caffeine and you can use the same
daphnia or a different daphnia
 Plot a graph and make a table for your results.

Results

Caffeine Mean(BPM) Standard Standard
concentration error(upper limit) error(lower limit)
(%)
0.00 320 331 308
0.02 328 343.8426 312.15732
0.03 338 342.5276 333.4724
0.05 338.6 612.4588 63.5412
0.06 344 356.802916 331.197084




Analysis and discussion