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applied science- unit 6 C and D -biology - distinction level
- Institution
- PEARSON (PEARSON)
this is the write up for the practical that i did. it is a combination of part C and D . it up to distinction level
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How does caffeine affect the heart rate of daphniaAuthor: chiamaka udoye
Abstract :
The experiment is aimed at investigation the effect of caffeine of the heart rate of daphnia. The daphnia was
transferred into the beaker using a pipette and one daphnia was used though out the experiment, it was placed in a
Petri dished to be observed under a microscope. The heart rate was recorded before the caffeine was introduced to
be used as a control value. the caffeine solution of varying concentration (0.03%, 0.05%, 1%, 2%) was then added
successively, allowing the Daphnia to acclimate for 5 minutes before heart rate measurement. The entire experiment
was repeated 3 times using the same daphnia and the result gotten was recorded into a table which is then used
calculate the average heart rate. The obtained data showed a clear correlation between caffeine concentration and
increased heart rate. The findings were consistent with the class average, indicating reliability. Statistical analysis
revealed no significant differences among the caffeine concentrations tested, contradicting the conclusion that
increasing caffeine concentration leads to higher heart rates in Daphnia .
Introduction:
Daphnia, also known as water fleas, are small crustaceans that can be found in freshwater habitats like ponds, lakes,
and streams. These organisms play a vital role in the food chain, providing a source of food for fish and other aquatic
animals. Due to their abundance and ease of culturing, Daphnia have been used in a wide variety of experiments,
including those focused on understanding how caffeine affects heart rate. One of the reasons why Daphnia are so
useful for bioassays is that they are cheap, easy, and sensitive to changes in water chemistry. As mentioned in
(Cornell.edu, 2009), Daphnia can be grown quickly and reach maturity in just a few days, making it possible to set up
experiments in a relatively short amount of time. Additionally, Daphnia are transparent, which allows researchers to
observe their internal organs without the need for dissection. This is particularly useful for experiments that focus on
changes in heart rate, as it is easy to observe the heart beating under a microscope. In addition to their ease of use,
Daphnia are also a good model organism for studying the effects of caffeine on heart rate due to their similarities to
humans. As stated in (Miguel Faria, 2022), Daphnia are highly sensitive animals with fundamental biological
responses that are remarkably similar to those of humans. This makes them a good model for testing the effects of
various recreational drugs, such as coffee, tobacco, and alcohol. Another advantage of using Daphnia in experiments
is that they are less developed than humans in terms of their nervous system.
The heart is a vital organ that moves blood throughout the body, giving cells nutrients and oxygen while also
removing waste. A number of things, including physical activity, stress, and specific substances, can affect the heart
rate, which is the number of times the heart beats per minute. Particularly, Numerous substances, including caffeine,
nicotine, and alcohol, have been shown to have different effects on heart rate. The reason why I am studying this
subject is to have an understanding of the effect of substances on the heart rate can be used to make an informed
medical treatment decision.
According to (Royal Society of Biology, 2019), some of the effects of noradrenaline and adrenaline on the heart are
mimicked by caffeine. Caffeine also raises the level of cAMP in the sinoatrial node via a different mechanism that
does not involve beta-1 adrenoceptors. When cAMP levels rise, the sinoatrial node becomes more electrically active,
depolarizes, and begins to "beat" more quickly. The heart is also affected by caffeine. Similar to how adrenaline and
noradrenaline act on the heart's main pumping chambers (ventricles), it has the potential to speed up the rate at
which each heartbeat contracts and relaxes. This means that along with beating more quickly, the heart's individual
beats are also linked to a greater volume of blood ejected into the circulation per unit time, raising cardiac output.
According to (Advent Health, 2021) provides additional insight into how caffeine affects the heart. As soon as
caffeine enters the bloodstream, it stimulates the central nervous system, causing an increase in heart rate. The
receptors in the cells within the heart are stimulated by caffeine, causing the heart rate to increase. The blood flow
also increases as the heartbeat quickens by about three beats per minute. This effect can begin within 15 minutes of
consuming caffeine and last for up to six hours.
, Hypothesis: if daphnia are exposed to caffeine, then their heart rate will increase as a result of the stimulant effect of
caffeine on the nervous system
The hypothesis that the heart rate of Daphnia increases when caffeine is consumed is based on the assumption that
caffeine, a known stimulant, has a similar effect on Daphnia's nervous system. Daphnia is a species of aquatic
crustacean that has a transparent exoskeleton, which makes it possible to see its internal organs, including the heart.
The heart of Daphnia is located in its head and pumps blood through its body. Caffeine is a stimulant that is known to
increase heart rate in humans, and it is expected to have a similar effect on Daphnia. When caffeine is introduced
into the environment of Daphnia, it is absorbed into its body through diffusion. As a result, the nervous system of
Daphnia is stimulated by caffeine, which causes an increase in the heart rate by speeding up heartbeats. To test this
hypothesis, an experiment can be performed where Daphnia are exposed to various concentrations of caffeine, and
their heart rates are measured and compared to a control group that is not exposed to caffeine. If Daphnia's heart
rate increases significantly when exposed to caffeine, it would provide evidence in favour of the theory.
Materials and Methods:
Equipment:
Caffeine solution, distilled water, microscope, stopwatch, Petri dishes, pipettes and cotton
Variables:
Control variable: microscope
Independent variable: the concentration of caffeine, the daphnia used
Dependent variable: the heart rate
method
Using a pipette, I transferred a small number of daphnia into a beaker
I then used the same pipette to extract 1 daphnia from the beaker and placed it into a Petri dish. Trying to be
quick as possible and not moving to much as to not cause stress
I placed the positioned the daphnia under a light microscope to monitor the heart rate.
I first counted the daphnia heart rate before the caffeine solution was added to know it control group
Then using the same daphnia, I added 0.03% of caffeine and waited 5 minutes to allow the daphnia to
Acculine to the caffeine solution then measured the heart rate
I then transferred the daphnia to a new Petr dish and added 0.05% caffine solution, allowing the daphnia to
Acculine from 5 minutes and then measured the heart rate. This was done using a timer at to measure 1
minute
Repeat step 6 again for the 1% and 2% caffeine solution
Repeat the whole experiment 3 times using different daphnia to make it more reliable, making sure to
record it in a suitable table and work out the average
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