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Applied Science Level 3 Unit 6 Investigative Project Learning Aim C&D
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Unit 6: investigative projectLearning aim D: review the investigative project using correct scientific principles
Mahdi Noori
Title: Investigating factors affecting the heart rate of Daphnia
Abstract
The following experiment is about the effect of various concentrations of caffeine on the heart rate of
daphnia. Caffeine is a stimulant chemical that causes the release of excitatory neurotransmitters when
the caffeine binds to receptors in the central nervous system. An increase in heart rate, stress and high
blood pressure can occur because of this. The purpose of this study is to see how caffeine affects the
heart and its rate. To improve the experiment, various caffeine concentrations are given. Daphnia are
chosen because their heart matches those of humans. According to the experiment, caffeine is a
stimulant.
Introduction
Aquatic organisms that live in freshwater lakes, rivers and ponds are referred to as "daphnia." They are
also called water fleas because of their jerky swimming style. For scientists and their study, they are a
good model organism. They have been used in lab tests for a long time, and one of the most typical
experiments scientists perform on them is to see what effects something has on a living thing's heart
rate. Daphnia has a myogenic heart, which is similar I the heart of a human. Scientists believe they will
behave in the same way that a human heart would behave. They have a translucent body which allows
the heartbeat to be seen easily.
Another reason why they are chosen is that daphnia mature fully within a few days of birth and are not
close to extinction if we use them in experiments. Furthermore more, they reproduce asexually, which
means that both male and female daphnia are not required to generate offspring. So, there is no need
to be concerned if the male daphnia dies during the experiment. They have a far less developed
neurological system than humans, hence they are less sensitive to pain.
Caffeine is a stimulant, which means it speeds up the passage of messages between the brain and the
rest of the body. Stimulatory neurotransmitters are released because of this. In addition, the nervous
system's activity has increased. The sum of these effects causes an increase in heart rate. Increased
caffeine intake will boost heart rate under normal circumstances, but a certain amount of caffeine will
cause the heart to stop pumping. Which eventually leads to death. if the heart is not revived.
Aim
To investigate the effect of caffeine on the heart rate of Daphnia
Hypothesis
The main objective of this experiment is to see how caffeine affects daphnia’s heart rate. As caffeine is a
stimulant, it does increase the heart rate of daphnia.
Dependent variable:
, Heart rate of daphnia
Independent variable:
Concentration of caffeine
Control variable:
Volume of solutions
Size of daphnia
Time
Stress of daphnia
The light intensity of the microscope
The temperature of the water
Equipment
Daphnia
Caffeine solution
Microscope
Paper towels
Stopwatch
Test tubes
Pipettes
Cotton wool
Cavity slides
Dropping pipettes
Method
1. Place a few strands of cotton wool on the cavity slide to prevent the Daphnia from moving
around and secure them in place.
2. Pick a Daphnia from a water pond using a pipette and place it on the cavity slide. Use a paper
towel to drain water around the Daphnia.
3. Add 1 or 2 drops of caffeine solution to the daphnia with a different pipette.
4. It is better to leave the daphnia for a few seconds/minutes so that the caffeine shows its effects.
5. Turn on the microscope, place the cavity slide, and position the daphnia where you can see its
heart properly.
6. Start a stopwatch and count the heartbeat between 1 minute to 5 minutes. And write down the
amount of heartbeat on a table.
7. Repeat this process with different concentrations of caffeine. You could use different Daphnia or
the same Daphnia.
8. Make a suitable graph and suitable table for your results in a suitable format.
Results
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